/ Language: English / Genre:sf

Diaspora

Грег Иган


Part One

Yatima surveyed the Doppler-shifted stars around the polis, following the frozen, concentric waves of color across the sky from expansion to convergence. Ve wondered what account they should give of themselves when they finally caught up with their quarry. They’d brought no end of questions to ask, but the flow of information couldn’t all be one-way. When the Transmuters demanded to know "Why have you followed us? Why have you come so far?", where should ve begin?

Yatima had read pre-Introdus histories told on a single level, bounded by the fictions that individuals were as indivisible as quarks, and planetary civilizations nothing less than self-contained universes. Neither vis own history nor the Diaspora’s would fit between those imaginary lines. The real world was full of larger structures, smaller structures, simpler and more complex structures than the tiny portion comprising sentient creatures and their societies, and it required a profound myopia of scale and similarity to believe that everything beyond this shallow layer could be ignored. It wasn’t just a question of choosing to bury yourself in a closed world of synthetic scapes; the fleshers had never been immune to this myopia, nor had the most outward-looking citizens. No doubt at some time in their history the Transmuters had suffered from it too.

Of course, the Transmuters would already be aware of the very large, very dead celestial machinery that had driven the Diaspora to Swift and beyond. Their question would be, "Why have you come so much further? Why have you left your own people behind?"

Yatima couldn’t speak for vis fellow traveler, but the answer for ver lay at the opposite end of the scale, in the realm of the very simple, and the very small.

1. Orphanogenesis

Konishi polis, Earth

23 387 025 000 000 CST

15 May 2975, 11:03:17.154 UT

The conceptory was non-sentient software, as ancient as Konishi polis itself. Its main purpose was to enable the citizens of the polis to create offspring: a child of one parent, or two, or twenty formed partly in their own image, partly according to their wishes, and partly by chance. Sporadically, though, every teratau or so, the conceptory created a citizen with no parents at all.

In Konishi, every home-born citizen was grown from a mind seed, a string of instruction codes like a digital genome. The first mind seeds had been translated from DNA nine centuries before, when the polis founders had invented the Shaper programming language to re-create the essential processes of neuroembryology in software. But any such translation was necessarily imperfect, glossing over the biochemical details in favor of broad, functional equivalence, and the full diversity of the flesher genome could not be brought through intact. Starting from a diminished trait pool, with the old DNA-based maps rendered obsolete, it was crucial for the conceptory to chart the consequences of new variations to the mind seed. To eschew all change would be to risk stagnation; to embrace it recklessly would he to endanger the sanity of every child.

The Konishi mind seed was divided into a billion fields: short segments, six bits long, each containing a simple instruction code. Sequences of a few dozen instructions comprised shapers: the basic subprograms employed during psychogenesis. The effects of untried mutations on fifteen million interacting shapers could rarely he predicted in advance; in most cases, the only reliable method would have been to perform every computation that the altered seed itself would have performed… which was no different from going ahead and sowing the seed, creating the mind, predicting nothing. The conceptory’s accumulated knowledge of its craft took the form of a collection of annotated maps of the Konishi mind seed. The highest-level maps were elaborate, multidimensional structures, dwarfing the seed itself by orders of magnitude. But there was one simple map which the citizens of Konishi had used to gauge the conceptory 's progress over the centuries; it showed the billion fields as lines of latitude, and the sixty-four possible instruction codes as meridians. Any individual seed could be thought of as a path which zig-zagged down the map from top to bottom, singling out an instruction code for every field along the way.

Where it was known that only one code could lead to successful psychogenesis, every route on the map converged on a lone island or a narrow isthmus, ocher against ocean blue. These infrastructure fields built the basic mental architecture every citizen had in common, shaping both the mind’s overarching design and the fine details of vital subsystems.

Elsewhere, the map recorded a spread of possibilities: a broad landmass, or a scattered archipelago. Trait fields offered a selection of codes, each with a known effect on the mind’s detailed structure, with variations ranging from polar extremes of innate temperament or aesthetics down to minute differences in neural architecture less significant than the creases on a flesher’s palm. They appeared in shades of green as wildly contrasting or as flatly indistinguishable as the traits themselves.

The remaining fields—where no changes to the seed had yet been tested, and no predictions could he made—were classified as indeterminate. Here, the one tried code, the known landmark, was shown as gray against white: a mountain peak protruding through a hand of clouds which concealed everything to the east or west of it. No more detail could be resolved from afar; whatever lay beneath the clouds could only he discovered firsthand.

Whenever the conceptory created an orphan, it set all the benignly mutable trait fields to valid codes chosen at random, since there were no parents to mimic or please. Then it selected a thousand indeterminate fields, and treated them in much the same fashion: throwing a thousand quantum dice to choose a random path through terra incognita. Every orphan was an explorer, sent to map uncharted territory.

And every orphan was the uncharted territory itself.

The conceptory placed the new orphan seed in the middle of the womb’s memory, a single strand of information suspended in a vacuum of zeroes. The seed meant nothing to itself; alone, it might as well have been the last stream of Morse, fleeing through the void past a distant star. But the womb was a virtual machine designed to execute the seed’s instructions, and a dozen more layers of software led down to the polis itself, a lattice of flickering molecular switches. A sequence of bits, a string of passive data, could do nothing, change nothing—but in the womb, the seed’s meaning fell into perfect alignment with all the immutable rules of all the levels beneath it. Like a punched card fed into a jacquard loom, it ceased to be an abstract message and became a part of the machine.

When the womb read the seed, the seed’s first shaper caused the space around it to be filled with a simple pattern of data: a single, frozen numerical wave train, sculpted across the emptiness like a billion perfect ranks of sand dunes. This distinguished each point from its immediate neighbors further up or down the same slope-but each crest was still identical to every other crest, each trough the same as every other trough. The womb’s memory was arranged as a space with three dimensions, and the numbers stored at each point implied a fourth. So these dunes were four-dimensional.

A second wave was added—running askew to the first, modulated with a slow steady rise—carving each ridge into a series of ascending mounds. Then a third, and a fourth, each successive wave enriching the pattern, complicating and fracturing its symmetries: defining directions, building up gradients, establishing a hierarchy of scales.

The fortieth wave plowed through an abstract topography bearing no trace of the crystalline regularity of its origins, with ridges and furrows as convoluted as the whorls of a fingerprint. Not every point had been rendered unique—but enough structure had been created to act as the framework for everything to come. So the seed gave instructions for a hundred copies of itself to he scattered across the freshly calibrated landscape.

In the second iteration, the womb read all of the replicated seeds—and at first, the instructions they issued were the same, everywhere. Then, one instruction called for the point where each seed was being read to jump forward along the hit string to the next field adjacent to a certain pattern in the surrounding data: a sequence of ridges with a certain shape, distinctive but not unique. Since each seed was embedded in different terrain, each local version of this landmark was situated differently, and the womb began reading instructions from a different part of every seed. The seeds themselves were all still identical, but each one could now unleash a different set of shapers on the space around it, preparing the foundations for a different specialized region of the psychoblast, the embryonic mind.

The technique was an ancient one: a budding flower’s nondescript stem cells followed a self-laid pattern of chemical cues to differentiate into sepals or petals, stamens or carpels; an insect pupa doused itself with a protein gradient which triggered, at different doses, the different cascades of gene activity needed to sculpt abdomen, thorax, or head. Konishi’s digital version skimmed off the essence of the process: divide up space by marking it distinctively, then let the local markings inflect the unwinding of all further instructions, switching specialized subprograms on and off—subprograms which in turn would repeat the whole cycle on ever finer scales, gradually transforming the first roughhewn structures into miracles of filigreed precision.

By the eighth iteration, the womb’s memory contained a hundred trillion copies of the mind seed; no more would he required. Most continued to carve new detail into the landscape around them—but some gave up on shapers altogether, and started running shriekers: brief loops of instructions which fed streams of pulses into the primitive networks which had grown up between the seeds. The tracks of these networks were just the highest ridges the shapers had built, and the pulses were tiny arrowheads, one and two steps higher. The shapers had worked in four dimensions, so the networks themselves were three-dimensional. The womb breathed life into these conventions, making the pulses race along the tracks like a quadrillion cars shuttling between the trillion junctions of a ten-thousand-tiered monorail.

Some shriekers sent out metronomic bit-streams; others produced pseudorandom stutters. The pulses flowed through the mazes of construction where the networks were still being formed—where almost every track was still connected to every other, because no decision to prune had yet been made. Woken by the traffic, new shapers started up and began to disassemble the excess junctions, preserving only those where a sufficient number of pulses was arriving simultaneously—choosing, out of all the countless alternatives, pathways which could operate in synchrony. There were dead ends in the networks-in-progress, too—but if they were traveled often enough, other shapers noticed, and constructed extensions. It didn’t matter that these first streams of data were meaningless; any kind of signal was enough to help whittle the lowest-level machinery of thought into existence.

In many polises, new citizens weren’t grown at all; they were assembled directly from generic subsystems. But the Konishi method provided a certain quasi-biological robustness, a certain seamlessness. Systems grown together, interacting even as they were being formed, resolved most kinds of potential mismatch themselves, with no need for an external mind-builder to fine-tune all the finished components to ensure that they didn’t clash.

Amidst all this organic plasticity and compromise, though, the infrastructure fields could still stake out territory for a few standardized subsystems, identical from citizen to citizen. Two of these were channels for incoming data—one for gestalt, and one for linear, the two primary modalities of all Konishi citizens, distant descendants of vision and hearing. By the orphan’s two-hundredth iteration, the channels themselves were fully formed, but the inner structures to which they fed their data, the networks for classifying and making sense of it, were still undeveloped, still unrehearsed.

Konishi polis itself was buried two hundred meters beneath the Siberian tundra, but via fiber and satellite links the input channels could bring in data from any forum in the Coalition of Polises, from probes orbiting every planet and moon in the solar system, from drones wandering the forests and oceans of Earth, from ten million kinds of scape or abstract sensorium. The first problem of perception was learning how to choose from this superabundance.

In the orphan psychoblast, the half-formed navigator wired to the controls of the input channels began issuing a stream of requests for information. The first few thousand requests yielded nothing but a monotonous stream of error codes; they were incorrectly formed, or referred to non-existent sources of data. But every psychoblast was innately biased toward finding the polis library (if not, it would have taken millennia) and the navigator kept trying until it hit on a valid address, and data flooded through the channels: a gestalt image of a lion, accompanied by the linear word for the animal.

The navigator instantly abandoned trial and error and went into a spasm of repetition, summoning the same frozen image of the lion again and again. This continued until even the crudest of its embryonic change discriminators finally stopped firing, and it drifted back toward experimentation.

Gradually, a half-sensible compromise evolved between the orphan’s two kinds of proto-curiosity: the drive to seek out novelty, and the drive to seek out recurring patterns. It browsed the library, learning how to bring in streams of connected information-sequential images of recorded motion, and then more abstract chains of cross-references-understanding nothing, but wired to reinforce its own behavior when it struck the right balance between coherence and change.

Images and sounds, symbols and equations, flooded through the orphan’s classifying networks, leaving behind, not the fine details—not the spacesuited figure standing on gray-and-white rock against a pitch black sky; not the calm, naked figure disintegrating beneath a gray swarm of nanomachines—but an imprint of the simplest regularities, the most common associations. The networks discovered the circle/sphere: in images of the sun and planets, in iris and pupil, in fallen fruit, in a thousand different artworks, artifacts, and mathematical diagrams. They discovered the linear word for "person," and bound it tentatively both to the regularities which defined the gestalt icon for "citizen," and to the features they found in common among the many images of fleshers and gleisner robots.

By the five-hundredth iteration, the categories extracted from the library’s data had given rise to a horde of tiny sub-systems in the input-classifying networks: ten thousand word-traps and image-traps, all poised and waiting to be sprung; ten thousand pattern-recognizing monomaniacs staring into the information stream, constantly alert for their own special targets.

These traps began to form connections with each other, using them at first just to share their judgments, to sway each other’s decisions. If the trap for the image of a lion was triggered, then the traps for its linear name, for the kind of sounds other lions had been heard to make, for common features seen in their behavior (licking cubs, pursuing antelope) all became hypersensitive. Sometimes the incoming data triggered a whole cluster of linked traps all at once, strengthening their mutual connections, but sometimes there was time for overeager associate traps to start firing prematurely. The lion shape has been recognized-and though the word "lion" has not yet been detected, the "lion" word-trap is tentatively firing… and so are the traps for cub-licking and antelope-chasing.

The orphan had begun to anticipate, to hold expectations.

By the thousandth iteration, the connections between the traps had developed into an elaborate network in its own right, and new structures had arisen in this network—symbols which could be triggered by each other as easily as by any data from the input channels. The lion image-trap, on its own, had merely been a template held up to the world to be declared a match or a mismatch a verdict without implications. The lion symbol could encode an unlimited web of implications—and that web could be tapped at any time, whether or not a lion was visible.

Mere recognition was giving way to the first faint hints of meaning.

The infrastructure fields had built the orphan standard output channels for linear and gestalt, but as yet the matching navigator, needed to address outgoing data to some specific destination in Konishi or beyond, remained inactive. By the two-thousandth iteration, symbols began to jostle for access to the output channels, regardless. They used their traps' templates to parrot the sound or image which each had learned to recognize—and it didn’t matter if they uttered the linear words "lion," "cub," "antelope" into a void, because the input and output channels were wired together, on the inside.

The orphan began to hear itself think.

Not the whole pandemonium; it couldn’t give voice—or even gestalt—to everything at once. Out of the myriad associations every scene from the library evoked, only a few symbols at a time could gain control of the nascent language production networks. And though birds were wheeling in the sky, and the grass was waving, and a cloud of dust and insects was rising up in the animals' wake—and more, much more… the symbols which won out before the whole scene vanished were:

"Lion chasing antelope."

Startled, the navigator cut off the flood of external data. The linear words cycled from channel to channel, distinct against the silence; the gestalt images summoned up the essence of the chase again and again, an idealized reconstruction shorn of all forgotten details.

Then the memory faded to black, and the navigator reached out to the library again.

The orphan’s thoughts themselves never shrank to a single orderly progression—rather, symbols fired in ever richer and more elaborate cascades—but positive feedback sharpened the focus, and the mind resonated with its own strongest ideas. The orphan had learned to single out one or two threads from the symbols' endless thousand-strand argument. It had learned to narrate its own experience.

The orphan was almost half a megatau old, now. It had a vocabulary of ten thousand words, a short-term memory, expectations stretching several tau into the future, and a simple stream of consciousness. But it still had no idea that there was such a thing in the world as itself.

The conceptory mapped the developing mind after every iteration, scrupulously tracing the effects of the randomized indeterminate fields. A sentient observer of the same information might have visualized a thousand delicate interlocking fractals, like tangled, feathery, zerogee crystals, sending out ever-finer branches to crisscross the womb as the fields were read and acted upon, and their influence diffused from network to network. The conceptory didn’t visualize anything; it just processed the data, and reached its conclusions.

So far, the mutations appeared to have caused no harm. Every individual structure in the orphan’s mind was functioning broadly as expected, and the traffic with the library, and other sampled data streams, showed no signs of incipient global pathologies.

If a psychoblast was found to be damaged, there was nothing in principle to stop the conceptory from reaching into the womb and repairing every last malformed structure, but the consequences could he as unpredictable as the consequences of growing the seed in the first place. Localized "surgery" sometimes introduced incompatibilities with the rest of the psychoblast, while alterations widespread and thorough enough to guarantee success could he self-defeating, effectively obliterating the original psychoblast and replacing it with an assembly of parts cloned from past healthy ones.

But there were risks, too, in doing nothing. Once a psychoblast became self-aware, it was granted citizenship, and intervention without consent became impossible. This was not a matter of mere custom or law; the principle was built into the deepest level of the polis. A citizen who spiraled down into insanity could spend teratau in a state of confusion and pain, with a mind too damaged to authorize help, or even to choose extinction. That was the price of autonomy: an inalienable right to madness and suffering, inseparable from the right to solitude and peace.

So the citizens of Konishi had programmed the conceptory to err on the side of caution. It continued to observe the orphan closely, ready to terminate psychogenesis at the first sign of dysfunction.

Not long after the five-thousandth iteration, the orphan’s output navigator began to fire—and a tug-of-war began. The output navigator was wired to seek feedback, to address itself to someone or something that showed a response. But the input navigator had long since grown accustomed to confining itself to the polis library, a habit which had been powerfully rewarded. Both navigators were wired with a drive to bring each other into alignment, to connect to the same address, enabling the citizen to listen and speak in the same place—a useful conversational skill. But it meant that the orphan’s chatter of speech and icons flowed straight back to the library, which completely ignored it.

Faced with this absolute indifference, the output navigator sent repressor signals into the change-discriminator networks, undermining the attraction of the library’s mesmerizing show, bullying the input navigator out of its rut. Dancing a weird chaotic lockstep, the two navigators began hopping from scape to scape, polis to polis, planet to planet. Looking for someone to talk to.

They caught a thousand random glimpses of the physical world along the way: a radar image of a dust storm sweeping across the sea of dunes ringing the north polar ice cap of Mars; the faint infrared plume of a small comet disintegrating in the atmosphere of Uranus—an event that had taken place decades before, but lingered in the satellite’s discriminating memory. They even chanced upon a real-time feed from a drone weaving its way across the East African savanna toward a pride of lions, but unlike the library’s flowing images this vision seemed intractably frozen, and after a few tau they moved on.

When the orphan stumbled on the address for a Konishi forum, it saw a square paved with smooth rhombuses of mineral blues and grays, arranged in a pattern dense with elusive regularities but never quite repeating itself. A fountain sprayed liquid silver toward a cloud-streaked, burnt-orange sky; as each stream broke apart into mirrored droplets halfway up its arc, the shiny globules deformed into tiny winged piglets which flew around the fountain, braiding each others' flight paths and grunting cheerfully before diving back into the pool. Stone cloisters ringed the square, the inner side of the walkway a series of broad arches and elaborately decorated colonnades. Some of the arches had been given unusual twists—Eschered or Kleined, skewed through invisible extra dimensions.

The orphan had seen similar structures in the library, and knew the linear words for most of them; the scape itself was so unremarkable that the orphan said nothing about it at all. And the orphan had viewed thousands of scenes of moving, talking citizens, but it was acutely aware of a difference here, though it could not yet grasp clearly what it was. The gestalt images themselves mostly reminded it of icons it had seen before, or the stylized fleshers it had seen in representational art: far more diverse, and far more mercurial, than real fleshers could ever be. Their form was constrained not by physiology or physics, but only by the conventions of gestalt—the need to proclaim, beneath all inflections and subtleties, one primary meaning: I am a citizen.

The orphan addressed the forum: "People."

The linear conversations between the citizens were public, but muted—degraded in proportion to distance in the scape—and the orphan heard only an unchanging murmur.

It tried again. "People!"

The icon of the nearest citizen—a dazzling multihued form like a stained-glass statue, about two delta high—turned to face the orphan. An innate structure in the input navigator rotated the orphan’s angle of view straight toward the icon. The output navigator, driven to follow it, made the orphan’s own icon—now a crude, unconscious parody of the citizen’s—turn the same way.

The citizen glinted blue and gold. Vis translucent face smiled, and ve said, "Hello, orphan."

A response, at last! The output navigator’s feedback detector shut off its scream of boredom, damping down the restlessness which had powered the search. It flooded the mind with signals to repress any system which might intervene and drag it away from this precious find.

The orphan parroted: "Hello, orphan."

The citizen smiled again—"Yes, hello"—then turned back to vis friends.

"People! Hello!"

Nothing happened.

"Citizens! People!"

The group ignored the orphan. The feedback detector backtracked on its satisfaction rating, making the navigators restless again. Not restless enough to abandon the forum, but enough to move within it.

The orphan darted from place to place, crying out: "People! Hello!" It moved without momentum or inertia, gravity or friction, merely tweaking the least significant bits of the input navigator’s requests for data, which the scape interpreted as the position and angle of the orphan’s point-of-view. The matching bits from the output navigator determined where and how the orphan’s speech and icon were merged into the scape.

The navigators learned to move close enough to the citizens to be easily heard. Some responded—"Hello, orphan"—before turning away. The orphan echoed their icons hack at them: simplified or intricate, rococco or spartan, mock-biological, mock-artifactual, forms outlined with helices of luminous smoke, or filled with vivid hissing serpents, decorated with blazing fractal encrustations, or draped in textureless black—but always the same biped, the same ape-shape, as constant beneath the riot of variation as the letter A in a hundred mad monks' illuminated manuscripts.

Gradually, the orphan’s input-classifying networks began to grasp the difference between the citizens in the forum and all the icons it had seen in the library. As well as the image, each icon here exuded a non-visual gestalt tag—a quality like a distinctive odor for a flesher, though more localized, and much richer in possibilities. The orphan could make no sense of this new form of data, but now its infotrope—a late-developing structure which had grown as a second level over the simpler novelty and pattern detectors—began to respond to the deficit in understanding. It picked up the tenuous hint of a regularity—every citizen’s icon, here, comes with a unique and unvarying tag—and expressed its dissatisfaction. The orphan hadn’t previously bothered echoing the tag, but now, spurred on by the infotrope, it approached a group of three citizens and began to mimic one of them, tag and all. The reward was immediate.

The citizen exclaimed angrily, "Don’t do that, idiot!"

"Hello!"

"No one will believe you if you claim to be me—least of all me. Understand? Now go away!" This citizen had metallic, pewter-gray skin. Ve flashed vis tag on and off for emphasis; the orphan did the same.

"No!" The citizen was now sending out a second tag, alongside the original. "See? I challenge you—and you can’t respond. So why bother lying?"

"Hello!"

"Go away"

The orphan was riveted; this was the most attention it had ever received.

"Hello, citizen!"

The pewter face sagged, almost melting with exaggerated weariness. "Don’t you know who you are? Don’t you know your own signature?"

Another citizen said calmly, "It must be the new orphan—still in the womb. Your newest co-politan, Inoshiro. You ought to welcome it."

This citizen was covered in short, golden-brown fur. The orphan said, "Lion." It tried mimicking the new citizen—and suddenly all three of them were laughing.

The third citizen said, "It wants to he you now, Gabriel."

The first, pewter-skinned citizen said, "If it doesn’t know its own name, we should call it idiot."

"Don’t be cruel. I could show you memories, little part-sibling." The third citizen’s icon was a featureless black silhouette.

"Now it wants to be Blanca."

The orphan started mimicking each citizen in turn. The three responded by chanting strange linear sounds which meant nothing—"Inoshiro! Gabriel! Blanca! Inoshiro! Gabriel! Blanca!"—just as the orphan sent out the gestalt images and tags.

Short-term pattern recognizers seized on the connection, and the orphan joined in the linear chanting, continued it for a while, when the others fell silent. But after a few repetitions the pattern grew stale.

The pewter-skinned citizen clasped vis hand to vis chest and said, "I’m Inoshiro."

The golden-furred citizen clasped vis hand to vis chest and said, "I’m Gabriel."

The black-silhouetted citizen gave vis hand a thin white outline to keep it from vanishing as ve moved it in front of vis trunk, and said, "I’m Blanca."

The orphan mimicked each citizen once, speaking the linear word they’d spoken, aping their hand gesture. Symbols had formed for all three of them, binding their icons, complete with tags, and the linear words together—even though the tags and the linear words still connected to nothing else.

The citizen whose icon had made them all chant "Inoshiro" said, "So far so good. But how does it get a name of its own.

The one with its tag bound to "Blanca" said, "Orphans name themselves."

The orphan echoed, "Orphans name themselves.'

The citizen bound to "Gabriel" pointed to the one bound to "Inoshiro," and said, "Ve is—?" The citizen bound to "Blanca" said "Inoshiro."

Then the citizen bound to "Inoshiro" pointed back at ver and said "Ve is ?" This time, the citizen bound to "Blanca" replied, "Blanca." The orphan joined in, pointing where the others pointed, guided by innate systems which helped make sense of the scape’s geometry, and completing the pattern easily even when no one else did.

Then the golden-furred citizen pointed at the orphan, and said: "Ve is?" The input navigator spun the orphan’s angle of view, trying to see what the citizen was pointing at. When it found nothing behind the orphan, it moved its point of view backward, closer to the golden-furred citizen-momentarily breaking step with the output navigator.

Suddenly, the orphan saw the icon it was projecting itself-a crude amalgam of the three Citizens' icons, all black fur and yellow metal-not just as the usual faint mental image from the cross-connected channels, but as a vivid scape-object beside the other three.

This was what the golden-furred citizen bound to "Gabriel" was pointing at.

The infotrope went wild. It couldn’t complete the unfinished regularity—it couldn’t answer the game’s question for this strange fourth citizen-but the hole in the pattern needed to he filled.

The orphan watched the fourth citizen change shape and color, out there in the scape… changes perfectly mirroring its own random fidgeting: sometimes mimicking one of the other three citizens, sometimes simply playing with the possibilities of gestalt. This mesmerized the regularity detectors for a while, but it only made the infotrope more restless.

The infotrope combined and recombined all the factors at hand, and set a short-term goal: making the pewter-skinned "Inoshiro" icon change, the way the fourth citizen’s icon was changing. This triggered a faint anticipatory firing of the relevant symbols, a mental image of the desired event. But though the image of a wiggling, pulsating citizen-icon easily won control of the gestalt output channel, it wasn’t the "Inoshiro" icon that changed—just the fourth citizen’s icon, as before.

 The input navigator drifted of its own accord back into the same location as the output navigator, and the fourth citizen abruptly vanished. The infotrope pushed the navigators apart again; the fourth citizen reappeared.

The "Inoshiro" citizen said, "What’s it doing?"

The "Blanca" citizen replied, "Just watch, and be patient. You might learn something."

A new symbol was already forming, a representation of the strange fourth citizen—the only one whose icon seemed bound by a mutual attraction to the orphan’s viewpoint in the scape, and the only one whose action the orphan could anticipate and control with such ease. So were all four citizens the same kind of thing-like all lions, all antelope, all circles… or not? The connections between the symbols remained tentative.

The "Inoshiro" citizen said, "I’m bored! Let some one else baby-sit it!" Ve danced around the group-taking turns imitating the "Blanca" and "Gabriel" icons, and reverting to vis original form. "What’s my name? I don’t know! What’s my signature? I don’t have one! I’m an orphan! I’m an orphan! I don’t even know how I look!"

When the orphan perceived the "Inoshiro" citizen taking on the icons of the other two, it almost abandoned its whole classification scheme in confusion. The "Inoshiro" citizen was behaving more like the fourth citizen, now—though vis actions still didn’t coincide with the orphan’s intentions.

The orphan’s symbol for the fourth citizen kept track of that citizen’s appearance and location in the scape, but it was also beginning to distill the essence of the orphan’s own mental images and short-term "goal" creating a summary of all the aspects of the orphan' state of mind which seemed to have some connection to the fourth citizen’s behavior. Few symbols possessed sharply defined boundaries, though; most were as permeable and promiscuous as plasmid-swapping bacteria. The symbol for the "Inoshiro" citizen copied some of the state-of-mind structures from the symbol for the fourth citizen, and began trying them out for itself.

At first, the ability to represent highly summarized "mental images" and "goals" was no help at all—because it was still linked to the orphan’s state of mind. The "Inoshiro" symbol’s blindly cloned machinery kept predicting that the "Inoshiro" citizen would behave according to the orphan’s own plans… and that never happened. In the face of this repeated failure, the links soon withered—and the tiny, crude model-of-a-mind left inside the "Inoshiro" symbol was set free to find the "Inoshiro" state-of-mind that best matched the citizen’s actual behavior.

The symbol tried out different connections, different theories, hunting for the one that made most sense… and the orphan suddenly grasped the fact that the "Inoshiro" citizen had been imitating the fourth citizen.

The infotrope seized on this revelation—and tried to make the fourth citizen mimic the "Inoshiro" citizen back.

The fourth citizen proclaimed, "I’m an orphan! I’m an orphan! I don’t even know how I look!"

The "Gabriel" citizen pointed at the fourth citizen and said, "Ve is an orphan!"

The "Inoshiro" citizen agreed wearily, "Ve is an orphan. But why does ve have to be this slow!"

Inspired—driven by the infotrope—the orphan tried playing the "Ve is-?" game again, this rime using the response "an orphan" for the fourth citizen. The other, confirmed the choice, and soon the words were bound to the symbol for the fourth citizen. When the orphan’s three friends left the scape, the fourth citizen remained. But the fourth citizen had exhausted vis ability to offer interesting surprises, so after pestering some of the other citizens to no avail, the orphan returned to the library.

The input navigator had learned the simplest indexing scheme used by the library, and when the infotrope hunted for ways to tie up the loose ends in the patterns half-formed in the scape, it succeeded in driving the input navigator to locations in the library which referred to the four citizens' mysterious linear words: Inoshiro, Gabriel, Blanca, and Orphan. There were streams of data indexed by each of these words, though none seemed to connect to the citizens themselves. The orphan saw so many images of fleshers, often with wings, associated with the word "Gabriel" that it built a whole symbol out of the regularities it found, but the new symbol barely overlapped with that of the golden-furred citizen.

The orphan drifted away from its infotrope-driven search many times; old addresses in the library, etched in memory, tugged at the input navigator. Once, viewing a scene of a grimy flesher child holding up an empty wooden bowl, the orphan grew bored and veered back toward more familiar territory. Halfway there, it came across a scene of an adult flesher crouching beside,, bewildered lion cub and lifting it into vis arms.

A lioness lay on the ground behind them, motionless and bloody. The flesher stroked the head of the cub. "Poor little Yatima."

Something in the scene transfixed the orphan. It whispered to the library, "Yatima. Yatima." It had never heard the word before, but the sound of it resonated deeply.

The lion cub mewed. The flesher crooned, "My poor little orphan." The orphan moved between the library and the scape with the orange sky and the flying-pig fountain. Sometimes its three friends were there, or other citizens would play with it for a while; sometimes there was only the fourth citizen.

The fourth citizen rarely appeared the same from visit to visit—ve tended to resemble the most striking image the orphan had seen in the library in the preceding few kilotau—but ve was still easy to identify: ve was the one who only became visible when the two navigators moved apart. Every time the orphan arrived in the scape, it stepped back from itself and checked out the fourth citizen. Sometimes it adjusted the icon, bringing it closer to a specific memory, or fine-tuning it according to the aesthetic preferences of the input classifying networks—biases first carved out by a few dozen trait fields, then deepened or silted-up by the subsequent data stream. Sometimes the orphan mimicked the flesher it had seen picking up the lion cub: tall and slender, with deep black skin and brown eyes, dressed in a purple robe.

And once, when the citizen bound to "Inoshiro" said with mock sorrow, "Poor little orphan, you still don’t have a name," the orphan remembered the scene, and responded, "Poor little Yatima."

The golden-furred citizen said, "I think it does, now.

From then on, they all called the fourth citizen "Yatima." They said it so many times, making such a fuss about it, that the orphan soon bound it to the symbol as strongly as "Orphan."

The orphan watched the citizen bound to "Inoshiro" chanting triumphantly at the fourth citizen: "Yatima? Yatima! Ha ha ha! I’ve got five parents, and five part, siblings, and I’ll always be older than you!"

The orphan made the fourth citizen respond, "Inoshiro! Inoshiro! Ha ha ha!"

But it couldn’t think what to say next. Blanca said, "The gleisners are trimming an asteroid—right now, in real time. Do you want to come see? Inoshiro’s there, Gabriel’s there. just follow me!"

Blanca’s icon put out a strange new tag, and then abruptly vanished. The forum was almost empty; there were a few regulars near the fountain, who the orphan knew would be unresponsive, and there was the fourth citizen, as always.

Blanca reappeared. "What is it? You don’t know how to follow me, or you don’t want to come?" The orphan’s language analysis networks had begun fine-tuning the universal grammar they encoded, rapidly homing in on the conventions of linear. Words were becoming more than isolated triggers for symbols, each with a single, fixed meaning; the subtleties of order, context, and inflection were beginning to modulate the symbols' cascades of interpretation. This was a request to know what the fourth citizen wanted.

"Play with me!" The orphan had learned to call the fourth citizen "I" or "me" rather than "Yatima," but that was just grammar, not self-awareness.

"I want to watch the trimming, Yatima."

"No! Play with me!" The orphan weaved around ver excitedly, projecting fragments of recent memories: Blanca creating shared scape objects—spinning numbered blocks, and brightly colored bouncing balls—and teaching the orphan how to interact with them.

"Okay, okay! Here’s a new game. I just hope you’re a fast learner."

Blanca emitted another extra tag—the same general flavor as before, though not identical—then vanished again… only to reappear immediately, a few hundred delta away across the scape. The orphan spotted ver easily, and followed at once.

Blanca jumped again. And again. Each time, ve sent out the new flavor of tag, with a slight variation, before vanishing. Just as the orphan was starting to find the game dull, Blanca began to stay out of the scape for a fraction of a tau before reappearing—and the orphan spent the time trying to guess where ve’d materialize next, hoping to get to the chosen spot first.

There seemed to be no pattern to it, though; Blanca’s solid shadow jumped around the forum at random, anywhere from the cloisters to the fountain, and the orphan’s guesses all failed. It was frustrating… but Blanca’s games had usually turned out to possess some kind of subtle order in the past, so the infotrope persisted, combining and recombining existing pattern detectors into new coalitions, hunting for a way to make sense of the problem. The tags! When the infotrope compared the memory of the raw gestalt data for the tags Blanca was sending with the address the innate geometry networks computed when the orphan caught sight of ver a moment later, parts of the two sequences matched up, almost precisely. Again and again. The infotrope bound the two sources of information together-recognizing them as two means of learning the same thing—and the orphan began jumping across the scape without waiting to see where Blanca reappeared.

The first time, their icons overlapped, and the orphan had to back away before it saw that Blanca really was there, confirming the success the infotrope had already brashly claimed. The second time, the orphan instinctively compensated, varying the tag address slightly to keep from colliding, as it had learned to do when pursuing Blanca by sight. The third time, the orphan beat ver to the destination.

"I win!"

"Well done, Yatima! You followed me!"

"I followed you!"

"Shall we go and see the trimming now? With Inoshiro and Gabriel?"

"Gabriel!"

"I’ll take that as a yes."

Blanca jumped, the orphan followed—and the cloistered square dissolved into a billion stars.

The orphan examined the strange new scape. Between them, the stars shone in almost every frequency from kilometer-long radio waves to high-energy gamma rays. The "color space" of gestalt could be extended indefinitely, and the orphan had chanced on a few astronomical images in the library which employed a similar palette, but most terrestrial scenes and most scapes never went beyond infrared and ultraviolet. Even the satellite views of planetary surfaces seemed drab and muted in comparison; the planets were too cold to blaze across the spectrum like this. There were hints of subtle order in the riot of color series of emission and absorption lines, smooth contours of thermal radiation but the infotrope, dazzled, gave in to the overload and simply let the data flow through it; analysis would have to wait for a thousand more clues. The stars were geometrically featureless—pointlike, distant, their scape addresses impossible to compute—but the orphan had a fleeting mental image of the act of moving toward them, and imagined, for an instant, the possibility of seeing them up close.

The orphan spotted a cluster of citizens nearby, and once it shifted its attention from the backdrop of stars it began to notice dozens of small groups scattered around the scape. Some of their icons reflected the ambient radiation, but most were simply visible by decree, making no pretense of interacting with the starlight.

Inoshiro said, "Why did you have to bring that along?"

As the orphan turned toward ver, it caught sight of a star far brighter than all the rest, much smaller than the familiar sight in the Earth’s sky, but unfiltered by the usual blanket of gases and dust.

"The sun?"

Gabriel said, "Yes, that’s the sun." The golden-furred citizen floated beside Blanca, who was visible as sharply as ever, darker even than the cool thin background radiation between the stars.

Inoshiro whined, "Why did you bring Yatima? It’s too young! It won’t understand anything!"

Blanca said, "Just ignore ver, Yatima."

Yatima! Yatima! The orphan knew exactly where Yatima was, and what ve looked like, without any need to part the navigators and check. The fourth citizen’s icon had stabilized as the tall flesher in the purple robe who’d adopted the lion cub, in the library.

Inoshiro addressed the orphan. "Don’t worry Yatima, I’ll try to explain it to you. If the gleisners didn’t trim this asteroid, then in three hundred thousand years—ten thousand teratau—there’d be a chance it might hit the Earth. And the sooner they trim it, the less energy it takes. But they couldn’t do it before, because the equations are chaotic, so they couldn’t model the approach well enough until now."

The orphan understood none of this. "Blanca wanted me to see the trimming! But I wanted to play a new game!"

Inoshiro laughed. "So what did ve do? Kidnap you?"

"I followed ver and ve jumped and jumped… and I followed ver!" The orphan made a few short jumps around the three of them, trying to illustrate the point, though it didn’t really convey the business of leaping right out of one scape into another.

Inoshiro said, "Ssh. Here it comes."

The orphan followed vis gaze to an irregular lump of rock in the distance-lit by the sun, one half in deep shadow—moving swiftly and steadily toward the loose assembly of citizens. The scape software decorated the asteroid’s image with gestalt tags packed with information about its chemical composition, its mass, its spin, its orbital parameters; the orphan recognized some of these flavors from the library, but it had no real grasp yet of what they meant. "One slip of the laser, and the fleshers die in pain!" Inoshiro’s pewter eyes gleamed.

Blanca said dryly, "And just three hundred millennia to try again."

Inoshiro turned to the orphan and added reassuringly, "But we’d he all right. Even if it wiped out Konishi on Earth, we’re backed-up all over the solar system."

The asteroid was close enough now for the orphan to compute its scape address and its size. It was still some hundred times more distant than the farthest citizen, but it was approaching rapidly. The waiting spectators were arranged in a roughly spherical shell, about ten times as large as the asteroid itself—and the orphan could see at once that if it maintained its trajectory, the asteroid would pass right through the center of that imaginary sphere.

Everyone was watching the rock intently. The orphan wondered what kind of game this was; a generic symbol had formed which encompassed all the strangers in the scape, as well as the orphan’s three friends, and this symbol had inherited the fourth citizen’s property of holding beliefs about objects which had proved so useful for predicting its behavior. Maybe people were waiting to see if the rock would suddenly jump at random, like Blanca had jumped? The orphan believed they were mistaken; the rock was not a citizen, it wouldn’t play games with them.

The orphan wanted everyone to know about the rock’s simple trajectory. It checked its extrapolation one more time, but nothing had changed; the bearing and speed were as constant as ever. The orphan lacked the words to explain this to the crowd… but maybe they could learn things by watching the fourth citizen, the way the fourth citizen had learned things from Blanca. The orphan jumped across the scape, straight into the path of the asteroid. A quarter of the sky became pocked and gray, an irregular hillock on the sunward side casting a hand of deep shadow across the approaching face. For an instant, the orphan was too startled to move—mesmerized by the scale, and the speed, and the awkward, purposeless grandeur of the thing—then it matched velocities with the rock, and led it back toward the crowd.

People began shouting excitedly, their words immune to the fictitious vacuum but degraded with distance by the scape, scrambled into a pulsating roar. The orphan turned away from the asteroid, and saw the nearest citizens waving and gesticulating.

The fourth citizen’s symbol, plugged directly into the orphan’s mind, had already concluded that the fourth citizen was tracing out the asteroid’s path in order to change what the other citizens thought. So the orphan’s model of the fourth citizen had acquired the property of having beliefs about what other citizens believed… and the symbols for Inoshiro, Blanca, Gabriel, and the crowd itself, snatched at this innovation to try it out for themselves.

As the orphan plunged into the spherical arena, it could hear people laughing and cheering. Everyone was watching the fourth citizen, though the orphan was finally beginning to suspect that no one had really needed to he shown the trajectory. As it looked back to check that the rock was still on course, a point on the hillock began to glow with intense infrared-and then erupted with light a thousand times brighter than the sunlit rock around it, and a thermal spectrum hotter than the sun itself. The orphan froze, letting the asteroid draw closer. A plume of incandescent vapor was streaming out of a crater in the hillock; the image was rich with new gestalt tags, all of them incomprehensible, but the infotrope burned a promise into the orphan’s mind: I will learn to understand them.

The orphan kept checking the scape addresses of the reference points it had been following, and it found a microscopic change in the asteroid’s direction. The flash of light—and this tiny shift in course were what everyone had been waiting to see? The fourth citizen had been wrong about what they knew, what they thought, what they wanted… and now they knew that? The implications rebounded between the symbols, models of minds mirroring models of minds, as the network hunted for sense and stability.

Before the asteroid could coincide with the fourth citizen’s icon, the orphan jumped back to its friends.

Inoshiro was furious. "What did you do that for? You ruined everything! You baby!"

Blanca asked gently, "What did you see, Yatima?"

"The rock jumped a little. But I wanted people to think… it wouldn’t."

"Idiot! You’re always showing off!"

Gabriel said, "Yatima? Why does Inoshiro think you flew with the asteroid?"

The orphan hesitated. "I don’t know what Inoshiro thinks."

The symbols for the four citizens shifted into a configuration they’d tried a thousand times before: the fourth citizen, Yatima, set apart from the rest, singled out as unique—this time, as the only one whose thoughts the orphan could know with certainty. And as the symbol network hunted for better ways to express this knowledge, circuitous connections began to tighten, redundant links began to dissolve.

There was no difference between the model of Yatima’s beliefs about the other citizens, buried inside the symbol for Yatima… and the models of the other citizens themselves, inside their respective symbols. The network finally recognized this, and began to discard the unnecessary intermediate stages. The model for Yatima’s beliefs became the whole, wider network of the orphan’s symbolic knowledge.

And the model of Yatima’s beliefs about Yatima’s mind became the whole model of Yatima’s mind: not a tiny duplicate, or a crude summary, just a tight bundle of connections looping back out to the thing itself.

The orphan’s stream of consciousness surged through the new connections, momentarily unstable with feedback: I think that Yatima thinks that I think that Yatima thinks…

Then the symbol network identified the last redundancies, cut a few internal links, and the infinite regress collapsed into a simple, stable resonance:

I am thinking

I am thinking that I know what I’m thinking.

Yatima said, "I know what I’m thinking."

Inoshiro replied airily, "What makes you think any one cares?"

For the five-thousand-and-twenty-third time, the conceptory checked the architecture of the orphan', mind against the polis’s definition of self-awareness.

Every criterion was now satisfied.

The conceptory reached into the part of itself which ran the womb, and halted it, halting the orphan. It modified the machinery of the womb slightly, allowing it to run independently, allowing it to he reprogrammed from within. Then it constructed a signature for the new citizen—two unique megadigit numbers, one private, one public—and embedded them in the orphan’s cypherclerk, a small structure which had lain dormant, waiting for these keys. It sent a copy of the public signature out into the polis, to be catalogued, to he counted.

Finally, the conceptory passed the virtual machine which had once been the womb into the hands of the polis operating system, surrendering all power over its contents. Cutting it loose, like a cradle set adrift in a stream. It was now the new citizen’s exoself: its shell, its non-sentient carapace. The citizen was free to reprogram it at will, but the polis would permit no other software to touch it. The cradle was unsinkable, except from within.

Inoshiro said, "Stop it! Who are you pretending to be now?"

Yatima didn’t need to part the navigators; ve knew vis icon hadn’t changed appearance, but was now sending out a gestalt tag. It was the kind ve’d noticed the citizens broadcasting the first time ve’d visited the flying-pig scape.

Blanca sent Yatima a different kind of tag; it contained a random number encoded via the public half of Yatima’s signature. Before Yatima could even wonder about the meaning of the tag, vis cypherclerk responded to the challenge automatically: decoding Blanca’s message, re-encrypting it via Blanca’s own public signature, and echoing it back as a third kind of tag. Claim of identity. Challenge. Response.

Blanca said, "Welcome to Konishi, Citizen Yatima." Ve turned to Inoshiro, who repeated Blanca’s challenge then muttered sullenly, "Welcome, Yatima." Gabriel said, "And Welcome to the Coalition of Polises."

Yatima gazed at the three of them, bemused, oblivious to the ceremonial words, trying to understand what had changed inside verself. Ve saw vis friends, and the stars, and the crowd, and sensed vis own icon… but even as these ordinary thoughts and perceptions flowed on unimpeded, a new kind of question seemed to spin through the black space behind them all. Who is thinking this? Who is seeing these stars, and these citizens? Who is wondering about these thoughts, and these sights?

And the reply came back, not just in words, but in the answering hum of the one symbol among the thousands that reached out to claim all the rest. Not to mirror every thought, but to bind them. To hold them together, like skin.

Who is thinking this?

I am.

2. Truth mining

Konishi polis, Earth

23 387 281 042 016 CST

18 May 2975, 10:10:39.170 UT

"What is it you’re having trouble with?"

Radiya’s icon was a fleshless skeleton made of twigs and branches, the skull carved from a knotted stump. Vis homescape was a forest of oak; they always met in the same clearing. Yatima wasn’t sure if Radiya spent much time here, or whether ve immersed verself completely in abstract mathematical spaces whenever ve was working, but the forest’s complex, arbitrary messiness made a curiously harmonious backdrop for the spartan objects they conjured up to explore.

"Spatial curvature. I still don’t understand where it comes from." Yatima created a translucent blob, floating between ver and Radiya at chest height, with half a dozen black triangles embedded in it. "If you start out with a manifold, shouldn’t you he able to impose any geometry you like on it?" A manifold was a space with nothing but dimension and topology; no angles, no distances, no parallel lines. As ve spoke, the blob stretched and bent, and the sides of the triangles swayed and undulated. "I thought curvature existed on a whole new level, a new set of rules you could write any way you liked. So you could choose zero curvature everywhere, if that' what you wanted." Ve straightened all the triangles into rigid, planar figures. "Now I’m not so sure. There are some simple two-dimensional manifolds, like a sphere, where I can’t see how to flatten the geometry. But I can’t prove that it’s impossible, either."

Radiya said, "What about a torus? Can you give a torus Euclidean geometry?"

"I couldn’t at first. But then I found a way."

"Show me."

Yatima banished the blob and created a torus, one delta wide and a quarter of a delta high, its white surface gridded with red meridians and blue circles of latitude. Ve’d found a standard tool in the library for treating the surface of any object as a scape; it re-scaled everything appropriately, forced notional light rays to follow the surface’s geodesics, and added a slight thickness so there was no need to become two-dimensional yourself. Politely offering the address so Radiya could follow, Yatima jumped into the torus’s scape.

They arrived standing on the outer rim—the torus’s "equator"—facing "south." With light rays clinging to the surface, the scape appeared boundless, though Yatima could clearly see the backs of both Radiya’s icon and vis own, one short revolution ahead, and ve could just make out a twice-distant Radiya through the gap between the two of them. The forest clearing was nowhere to be seen; above them was nothing but blackness.

Looking due south the perspective was very nearly linear, with the red meridians wrapping the torus appearing to converge toward a distant vanishing point. But to the east and west the blue lines of latitude—which seemed almost straight and parallel nearby—appeared to veer apart wildly as they approached a critical distance. Light rays circumnavigating the torus around the outer rim reconverged, as if focused by a magnifying lens, at the point directly opposite the place where they started out—so the vastly distended image of one tiny spot on the equator, exactly halfway around the torus, was hogging the view and pushing aside the image of everything north or south of it. Beyond the halfway mark the blue lines came together again and exhibited something like normal perspective for a while, before they came full circle and the effect was repeated. But this time the view beyond was blocked by a wide band of purple with a thin rim of black on top, stretching across the horizon: Yatima’s own icon, distorted by the curvature. A green and brown streak was also visible, partly obscuring the purple and black one, if Yatima looked directly away from Radiya.

"The geometry of this embedding is non-Euclidean, obviously." Yatima sketched a few triangles on the surface at their feet. "The sum of the angles of a triangle depends on where you put it: more than 180 degrees here, near the outer rim, but less than 180 near the inner rim. In between, it almost balances out."

Radiya nodded. "All right. So how do you balance it out everywhere without changing the topology?"

Yatima sent a stream of tags to the scape object, and the view around them began to he transformed. Their smeared icons on the horizon to the east and west began to shrink, and the blue lines of latitude began to straighten out. To the south, the narrow region of linear perspective was expanding rapidly. "If you bend a cylinder into a torus, the lines parallel to the cylinder’s axis get stretched into different-sized circles; that’s where the curvature really comes from. And if you tried to keep all those circles the same size, there’d be no way to keep them apart; you’d crush the cylinder flat in the process. But that’s only true in three dimensions."

The grid lines were all straight now, the perspective perfectly linear everywhere. They appeared to he standing on a boundless plane, with only the repeated images of their icons to reveal otherwise. The triangles had straightened out, too; Yatima made two identical copies of one of them, then maneuvered the three together into a fan that showed the angles summing to 180 degrees. "Topologically, nothing’s changed; I haven’t made any cuts or joins in the surface. The only difference is…"

Ve jumped back to the forest clearing. The torus appeared to have been transformed into a short cylindrical band; the large blue circles of latitude were all of equal size now-but the smaller red circles, the meridians, looked like they’d been flattened into straight lines. "I rotated each meridian 90 degrees, into a fourth spatial dimension. They only look flat because we’re seeing them edge-on." Yatima had rehearsed the trick with a lower-dimensional analogue: taking the band between a pair of concentric circles and twisting it 90 degrees out of the plane, standing it up on its edge; the extra dimension created room for the entire band to have a uniform radius. With a torus it was much the same; every circle of latitude could have the same radius, so long as they were given different "heights" in a fourth dimension to keep them apart. Yatima re-colored the whole torus in smoothly varying shades of green to reveal the hidden fourth coordinate. The inner and outer surfaces of the "cylinder" only matched colors at the top and bottom rims, "—here they met up in the fourth dimension; elsewhere, different hues on either side showed that they remained separated.

Radiya said, "Very nice. Now can you do the same for a sphere?"

Yatima grimaced with frustration. "I’ve tried! Intuitively, it just looks impossible… but I would have said the same thing about the torus, before I found the right trick." Ve created a sphere as ve spoke, then deformed it into a cube. No good, though—that was just sweeping all the curvature into the singularities of the corners, it didn’t make it go away.

"Okay. Here’s a hint." Radiya turned the cube back into a sphere, and drew three great circles on it in black: an equator, and two complete meridians 90 degrees apart.

"What have I divided the surface into?"

"Triangles. Right triangles." Four in the northern hemisphere, four in the south.

"And whatever you do to the surface—bend it, stretch it, twist it into a thousand other dimensions—you’ll always be able to divide it up the same way, won’t you? Eight triangles, drawn between six points?"

Yatima experimented, deforming the sphere into a succession of different shapes. "I think you’re right. But how does that help?"

Radiya remained silent. Yatima made the object transparent, so ve could see all the triangles at once. They formed a kind of coarse mesh, a six-pointed net, a closed bag of string. Ve straightened all twelve lines, which certainly flattened the triangles-but it transformed the sphere into an octahedral diamond, which was just as bad as a cube. Each face of the diamond was perfectly Euclidean, but the six sharp points were like infinitely concentrated repositories of curvature.

Ve tried smoothing and flattening the six points. That was easy—but it made the eight triangles as bowed and non-Euclidean as they’d been on the original sphere. It seemed "obvious" that the points and the triangles could never be made flat simultaneously… but Yatima still couldn’t pin down the reason why the two goals were irreconcilable. Ve measured the angles where four triangles met, around what had once been a point of the diamond: 90, 90, 90, 90. That much made perfect sense: to lie flat, and meet nicely without any gaps, they had to add up to 360 degrees. Ve reverted to the unblunted diamond, and measured the same angles again: 60, 60, 60, 60. A total of 240 was too small to lie flat; anything less than a full circle forced the surface to roll up like the point of a cone…

That was it! That was the heart of the contradiction! Every vertex needed angles totaling 360 degrees around it, in order to lie flat… while every flat, Euclidean triangle supplied just 180 degrees. Half as much. So if there’d been exactly twice as many triangles as vertices, everything would have added up perfectly-but with six vertices and only eight triangles, there wasn’t enough flatness to go round.

Yatima grinned triumphantly, and recounted vis chain of reasoning. Radiya said calmly, "Good. You’ve just discovered the Gauss-Bonnet Theorem, linking the Euler number and total curvature."

"Really?" Yatima felt a surge of pride; Euler and Gauss were legendary miners—long-dead fleshers, but their skills had rarely been equaled.

"Not quite." Radiya smiled slightly. "You should look up the precise statement of it, though; I think you’re ready for a formal treatment of Riemannian spaces. But if it all starts to seem too abstract, don’t be afraid to back off and play around with some more examples."

"Okay." Yatima didn’t need to be told that the lesson was over. Ve raised a hand in a gesture of thanks, then withdrew vis icon and viewpoint from the clearing.

For a moment Yatima was scapeless, input channels isolated, alone with vis thoughts. Ve knew ve still didn’t understand curvature fully—there were dozens of other ways to think about it—but at least ve’d grasped one more fragment of the whole picture.

Then ve jumped to the Truth Mines.

Ve arrived in a cavernous space with walls of dark rock, aggregates of gray igneous minerals, drab brown clays, streaks of rust red. Embedded in the floor of the cavern was a strange, luminous object: dozens of floating sparks of light, enclosed in an elaborate set of ethereal membranes. The membranes formed nested, concentric families, Daliesque onion layers—each series culminating in a bubble around a single spark, or occasionally a group of two or three. As the sparks drifted, the membranes flowed to accommodate them, in such a way that no spark ever escaped a single level of enclosure.

In one sense, the Truth Mines were just another indexscape. Hundreds of thousands of specialized selections of the library’s contents were accessible in similar ways—and Yatima had climbed the Evolutionary Tree, hopscotched the Periodic Table, walked the avenue-like Timelines for the histories of fleshers, gleisners, and citizens. Half a megatau before, ve’d swum through the Eukaryotic Cell; every protein, every nucleotide, even carbohydrate drifting through the cytoplasm had broadcast gestalt tags with references to everything the library had to say about the molecule in question.

In the Truth Mines, though, the tags weren’t just references; they included complete statements of the particular definitions, axioms, or theorems the objects represented. The Mines were self-contained: every mathematical result that fleshers and their descendants had ever proven was on display in its entirety. The library’s exegesis was helpful—but the truths themselves were all here.

The luminous object buried in the cavern floor broadcast the definition of a topological space: a set of points (the sparks), grouped into "open subsets" (the contents of one or more of the membranes) which specified how the points were connected to each other—without appealing to notions like "distance" or "dimension." Short of a raw set with no structure at all, this was about as basic as you could get: the common ancestor of virtually every entity worthy of the name "space," however exotic. A single tunnel led into the cavern, providing a link to the necessary prior concepts, and half a dozen tunnels led out, slanting gently "down" into the bedrock, pursuing various implications of the definition. Suppose T is a topological space… then what follows? These routes were paved with small gemstones, each one broadcasting an intermediate result on the way to a theorem. Every tunnel in the Mines was built from the steps of a watertight proof; every theorem, however deeply buried, could be traced back to every one of its assumptions. And to pin down exactly what was meant by a "proof," every field of mathematics used its own collection of formal systems: sets of axioms, definitions, and rules of deduction, along with the specialized vocabulary needed to state theorems and conjectures precisely.

When ve’d first met Radiya in the Mines, Yatima had asked ver why some non-sentient program couldn’t just take each formal system used by the miners and crank out all its theorems automatically sparing citizens the effort.

Radiya had replied, "Two is prime. Three is prime. Five is prime. Seven is prime. Eleven is prime. Thirteen is prime. Seventeen is-"

"Stop!"

"If I didn’t get bored, I could go on like that until the Big Crunch, and discover nothing else."

"But we could run a few billion programs at once, all mining in different directions. It wouldn’t matter if some of them never found anything interesting."

"Which different directions would you choose?"

"I don’t know. All of them?"

"A few billion blind moles won’t let you do that. Suppose you have just one axiom, taken as given, and ten valid logical steps you can use to generate new statements. After one step, you have ten truths to explore." Radiya had demonstrated, building a miniature, branching mine in the space in front of Yatima. "After ten steps, you have ten billion, ten to the tenth power." The fan of tunnels in the toy mine was already an unresolvable smear-but Radiya filled them with ten billion luminous moles, making the coal face glow strongly. "After twenty steps, you have ten to the twentieth. Too many to explore at once, by a factor of ten billion. How are you going to choose the right ones? Or would you time-share the moles between all of these paths—slowing them down to the point of uselessness?" The moles spread their light out proportionately-and the glow of activity became invisibly feeble. "Exponential growth is a curse in all its forms. You know it almost wiped out the fleshers? If we were insane enough, we could try turning the whole planet—or the whole galaxy—into some kind of machine able to exert the necessary brute computational force… but even then, I doubt we’d reach Fermat’s Last Theorem before the end of the universe."

Yatima had persisted. "You could make the programs more sophisticated. More discriminating. Let them generalize from examples, form conjectures… aim for proofs."

Radiya had conceded, "Perhaps it could be done. Some fleshers tried that approach before the Introdus—and if you’re short-lived, slow, and easily distracted, it almost makes sense to let unthinking software find the lodes you’d never hit before you died. For us, though… Why should we sacrifice the opportunity for pleasure?"

Now that ve’d experienced Truth Mining for verself, Yatima could only agree. There was nothing in any scape or library file, any satellite feed or drone image, more beautiful than mathematics. Ve sent the scape a query tag, and it lit the way to the Gauss-Bonnet Theorem with an azure glow for vis viewpoint only. Ve floated off slowly down one of the tunnels, reading all the tags from the jeweled path.

Learning was a strange business. Ve could have had vis exoself wire all this raw information straight into vis mind, in an instant—ve could have engulfed a complete copy of the Truth Mines, like an amoeba ingesting a planet—but the facts would have become barely more accessible than they already were, and it would have done nothing to increase vis understanding. The only way to grasp a mathematical concept was to see it in a multitude of different contexts, think through dozens of specific examples, and find at least two or three metaphors to power intuitive speculations. Curvature means the angles of a triangle might not add up to 180 degrees. Curvature means you have to stretch or shrink a plane non-uniformly to make it wrap a surface. Curvature means no room for parallel lines—or room for far more than Euclid ever dreamt of. Understanding an idea meant entangling it so thoroughly with all the other symbols in your mind that it changed the way you thought about everything.

Still, the library was full of the ways past miners had fleshed out the theorems, and Yatima could have had those details grafted in alongside the raw data, granting ver the archived understanding of thousands of Konishi citizens who’d traveled this route before. The right mind grafts would have enabled ver effortlessly to catch up with all the living miners who were pushing the coal face ever deeper in their own inspired directions… at the cost of making ver, mathematically speaking, little more than a patchwork clone of them, capable only of following in their shadows.

If ve ever wanted to be a miner in vis own right making and testing vis own conjectures at the coal face, like Gauss and Euler, Riemann and Levi-Civita, deRham and Cartan, Radiya and Blanca, then Yatima knew there were no shortcuts, no alternatives to exploring the Mines firsthand. Ve couldn’t hope to strike out in a fresh direction, a route no one had ever chosen before, without a new take on the old results. Only once ve’d constructed vis own map of the Mines—idiosyncratically crumpled and stained, adorned and annotated like one else’s—could ve begin to guess where the next rich vein of undiscovered truths lay buried.

Yatima was back in the savanna of vis homescape, playing with a torus crisscrossed with polygons, when Inoshiro sent a calling card; the tag entered the scape like a familiar scent on the wind. Yatima hesitated—ve was happy with what ve was doing, ve didn’t really want to be interrupted—but then ve relented, replying with a welcoming tag and granting Inoshiro access to the scape.

"What’s that ugly piece of crap?" Inoshiro gazed contemptuously at the minimalist torus. Ever since ve’d started visiting Ashton-Laval, ve seemed to have taken on the mantle of arbiter of scape aesthetics. Everything Yatima had seen in vis homescape wriggled ceaselessly, glowed across the spectrum, and had a fractal dimension of at least two point nine.

"A sketch of the proof that a torus has zero total curvature. I’m thinking of making it a permanent fixture."

Inoshiro groaned. "The establishment have really got their hooks into you. Orphan see, orphan do."

Yatima replied serenely, "I’ve decomposed the surface into polygons. The number of faces, minus the number of edges, plus the number of vertices—the Euler number—is zero."

"Not for long." Inoshiro scrawled a line across the object, defiantly bisecting one of the hexagons.

"You’ve just added one new face and one new edge. That cancels out exactly."

Inoshiro carved a square into four triangles.

"Three new faces, minus four new edges, plus one new vertex. Net change: zero."

"Mine fodder. Logic zombie." Inoshiro opened vis mouth and spewed out some random tags of propositional calculus.

Yatima laughed. "If you’ve got nothing better to do than insult me…" Ve began emitting the tag for imminent withdrawal of access.

"Come and see Hashim’s new piece."

"Maybe later." Hashim was one of Inoshiro’s Ashton-Laval artist friends. Yatima found most of their work bewildering, though whether it was the interpolis difference in mental architecture or just vis own personal taste, ve wasn’t sure. Certainly, Inoshiro insisted that it was all "sublime."

"It’s real time, ephemeral. Now or never."

"Not true: you could record it for me, or I could send a proxy—"

Inoshiro stretched vis pewter face into an exaggerated scowl. "Don’t be such a philistine. Once the artist decides the parameters, they’re sacrosanct—"

"Hashim’s parameters are just incomprehensible. Look, I know I won’t like it. You go."

Inoshiro hesitated, slowly letting vis features shrink back to normal size. "You could appreciate Hashim’s work, if you wanted to. If you ran the right outlook."

Yatima stared at ver. "Is that what you do?"

"Yes." Inoshiro stretched out vis hand, and a flower sprouted from the palm, a green-and-violet orchid which emitted an Ashton-Laval library address. "I didn’t call you before, because you might have told Blanca… and then it would have got back to one of my parents. And you know what they’re like."

Yatima shrugged. "You’re a citizen, it’s none of their business."

Inoshiro rolled vis eyes and gave ver vis best martyred look. Yatima doubted that ve’d ever understand families: there was nothing any of Inoshiro’s relatives could do to punish ver for using the outlook, let alone actually stop ver. All reproving messages could he filtered out; all family gatherings that turned into haranguing sessions could he instantly deserted. Yet Blanca’s parents—three of them Inoshiro’s—had badgered ver into breaking up with Gabriel (if only temporarily); the prospect of exogamy with Carter-Zimmerman was apparently beyond the pale. Now that they were together again, Blanca (for some reason) had to avoid Inoshiro as well as the rest of the family—and presumably Inoshiro no longer feared that vis part-sibling would blab.

Yatima was a little wounded. "I wouldn’t have told Blanca, if you’d asked me not to."

"Yeah, yeah. Do you think I don’t remember? Ve practically adopted you."

"Only when I was in the womb!" Yatima still liked Blanca very much, but they didn’t even see each other all that often, now.

Inoshiro sighed. "Okay: I’m sorry I didn’t tell you sooner. Now are you going to come see the piece?"

Yatima sniffed the flower again, warily. The Ashton-Laval address smelt distinctly foreign… but that was just unfamiliarity. Ve had vis exoself take a copy of the outlook and scrutinize it carefully. Yatima knew that Radiya, and most other miners, used outlooks to keep themselves focused on their work, gigatau after gigatau. Any citizen with a mind broadly modeled on a flesher’s was vulnerable to drift: the decay over time of even the most cherished goals and values. Flexibility was an essential part of the flesher legacy, but after a dozen computational equivalents of the pre-Introdus lifespan, even the most robust personality was liable to unwind into an entropic mess. None of the polises' founders had chosen to build predetermined stabilizing mechanisms into their basic designs, though, lest the entire species ossify into tribes of self-perpetuating monomaniacs, parasitized by a handful of memes. It was judged far safer for each citizen to he free to choose from a wide variety of outlooks: software that could run inside your exoself and reinforce the qualities you valued most, if and when you felt the need for such an anchor. The possibilities for short-term cross-cultural experimentation were almost incidental.

Each outlook offered a slightly different package of values and aesthetics, often built up from the ancestral reasons-to-be-cheerful that still lingered to some degree in most citizens' minds: Regularities and periodicities—rhythms like days and seasons. Harmonies and elaborations, in sounds and images, and in ideas. Novelty. Reminiscence and anticipation. Gossip, companionship, empathy, compassion. Solitude and silence. There was a continuum which stretched all the way from trivial aesthetic preferences to emotional associations to the cornerstones of morality and identity.

Yatima had vis exoself’s analysis of the outlook appear in the scape in front of ver as a pair of before-and-after maps of vis own most affected neural structures. 

The maps were like nets, with spheres at every junction to represent symbols; proportionate changes in the symbols' size showed how the outlook would tweak them.

"Death gets a tenfold boost? Spare me."

"Only because it’s so underdeveloped initially."

Yatima shot ver a poisonous look, then rendered the snaps private, and stood examining them with an air of intense concentration.

"Make up your mind; it’s starting soon."

"You mean make my mind Hashim’s?"

"Hashim doesn’t use an outlook."

"So it’s all down to raw artistic talent? Isn’t that what they all say?"

"Just… make a decision."

Vis exoself’s verdict on the potential for parasitism was fairly sanguine, though there could be no guarantees. If ve ran the outlook for a few kilotau, ve ought to be able to stop.

Yatima made a matching flower grow from vis own palm. "Why do you keep talking me into these crazy stunts?"

Inoshiro’s face formed the pure gestalt sign for unappreciated benefactor. "If I don’t save you from the Mines, who will?"

Yatima ran the outlook. At once, certain features of the scape seized vis attention: a thin streak of cloud in the blue sky, a cluster of distant trees, the wind rippling through the grass nearby. It was like switching from one gestalt color map to another, and seeing some objects leap out because they’d changed more than the rest. After a moment the effect died down, but Yatima still felt distinctly modified; the equilibrium had shifted in the tug-of-war between all the symbols in vis mind, and the ordinary buzz of consciousness had a slightly different tone to it.

"Are you okay?" Inoshiro actually looked concerned, and Yatima felt a rare, raw surge of affection for ver. Inoshiro always wanted to show ver what ve’d found in vis endless fossicking through the Coalition’s possibilities—because ve really did want ver to know what the choices were.

"I’m still myself. I think."

"Pity." Inoshiro sent the address, and they jumped into Hashim’s artwork together.

Their icons vanished; they were pure observers. Yatima found verself gazing at a red-tinged cluster of pulsing organic parts, a translucent confusion of fluids and tissue. Sections divided, dissolved, re-organized. It looked like a flesher embryo—though not quite a realist portrait. The imaging technique kept changing, revealing different structures: Yatima saw hints of delicate limbs and organs caught in slices of transmitted light; a stark silhouette of bones in an X-ray flash; the finely branched network of the nervous system bursting into view as a filigreed shadow, shrinking from myelin to lipids to a scatter of vesicled neurotransmitters against a radio-frequency MRI chirp.

There were two bodies, now. Twins? One was larger, though—sometimes much larger. The two kept changing places, twisting around each other, shrinking or growing in stroboscopic leaps while the wavelengths of the image stuttered across the spectrum.

One flesher child was turning into a creature of glass, nerves and blood vessels vitrifying into optical fibers. A sudden, startling white-light image showed living, breathing Siamese twins, impossibly transected to expose raw pink-and-gray muscles working side-by-side with shape-memory alloys and piezoelectric actuators, flesher and gleisner anatomies interpenetrating. The scene spun and morphed into a lone robot child in a flesher’s womb; spun again to show a luminous map of a citizen’s mind embedded in the same woman’s brain; zoomed out to place her, curled, in a cocoon of optical and electronic cables. Then a swarm of nanomachines burst through her skin, and everything scattered into a cloud of gray dust. Two flesher children walked side-by-side, hand-in-hand. Or father and son, gleisner and flesher, citizen and gleisner… Yatima gave up trying to pin them down, and let the impressions flow through ver. The two figures strode calmly along a city’s main street, while towers rose and crumbled around them, jungle and desert advanced and retreated.

The artwork, unbidden, sent Yatima’s viewpoint wheeling around the figures. Ve saw them exchanging glances, touches, kisses—and blows, awkwardly, their right arms fused at the wrists. Making peace and melting together. The smaller lifting the larger onto vis shoulders then the passenger’s height flowing down to the hearer like an hourglass’s sand.

They were parent and child, siblings, friends, lovers, species, and Yatima exulted in their companionship. Hashim’s piece was a distillation of the idea of friendship, within and across all borders. And whether it was all down to the outlook or not, Yatima was glad to he witnessing it, taking some part of it inside verself before every image dissolved into nothing but a flicker of entropy in Ashton-Laval’s coolant flow.

The scape began moving Yatima’s viewpoint away from the pair. For a few tau ve went along with this, but the whole city had decayed into a flat, fissured desert, so apart from the retreating figures there was nothing to be seen. Ve jumped hack to them-only to find that ve had to keep advancing vis coordinates just to stay in place. It was a strange experience: Yatima possessed no sense of touch, or balance, or proprioception—the Konishi design eschewed such delusions of corporeality-but the scape’s attempt to "push" ver away, and the need to accelerate against it, seemed so close to a physical struggle that ve could almost believe ve’d been embodied.

The figure facing Yatima aged suddenly, cheeks hollowing, eyes filming over. Yatima moved around to try to see the other’s face—and the scape sent ver flying across the desert, this time in the opposite direction, Ve fought vis way back to the… mother and daughter, then decaying robot and gleaming new one… and though the two remained locked together, hand-in-hand, Yatima could all but feel the force trying to tear them apart.

Ve watched flesh hand gripping skin-and-hones, metal gripping flesh, ceramic gripping metal. All of them slowly slipping. Yatima looked into the eyes of each figure; while everything else flowed and changed, their gazes remained locked together.

The scape split in two, the ground opened up, the sky divided. The figures were parted. Yatima was flung away from them, back into the desert with a force, now, that ve could not oppose. Ve saw them in the distance—twins again, of uncertain species, reaching out desperately across the empty space growing between them. Arms outstretched, fingertips almost brushing.

Then the halves of the world rushed apart. Someone bellowed with rage and grief.

The scape decayed into blackness before Yatima understood that the cry had been vis own.

The forum with the flying-pig fountain had been abandoned long ago, but Yatima had planted a copy from the archives in vis homescape, the cloistered square marooned in the middle of a vast expanse of parched scrubland. Empty, it looked at once too large and too small. A few hundred delta away, a copy (not to scale) of the asteroid ve’d watched being trimmed was buried in the ground. At one point Yatima had envisioned a vast trail of similar mementos stretching across the savanna, a map ve could fly over whenever ve wanted to review the turning points in vis life… but then the whole idea had begun to seem childish. If the things ve’d seen had changed ver, they’d changed ver; there was no need to re-create them as monuments. Ve’d kept the forum because ve genuinely liked to visit it—and the asteroid out of the sheer perverse pleasure of resisting the urge to tidy it away.

Yatima stood by the fountain for a while, watching its silver liquid effortlessly mock the physics it half-obeyed. Then ve re-created the octahedral diamond, the six-pointed net from vis lesson with Radiya, beside it. That physics meant nothing in the polises had always been clear to ver, as it was to most citizens; Gabriel disagreed, of course, but that was just Carter-Zimmerman doctrine talking. The fountain could ignore the laws of fluid dynamics just as easily as it could conform to them. Everything it did was simply arbitrary; even the perfect gravitational parabola of the start of each stream, before the piglets were formed, was nothing but an aesthetic choice and the aesthetic itself was nothing but the vestigial influence of flesher ancestry.

The diamond net was different, though. Yatima played with the object, deforming it wildly, stretching and twisting it beyond recognition. It was infinitely malleable… and yet a few tiny constraints on the changes ve could make to it rendered it, in a sense, unchangeable. However much ve distorted its shape, however many extra dimensions ve invoked, this net would never lie flat. Ve could replace it with something else entirely such as a net which wrapped a torus and then lay that new net flat… but that would have been as meaningless as creating a non-sentient, Inoshiro-shaped object, dragging it into the Truth Mines, and then claiming that ve’d succeeded in persuading vis real friend to come along.

Polis citizens, Yatima decided, were creatures of mathematics; it lay at the heart of everything they were, and everything they could become. However malleable their minds, in a sense they obeyed the same kind of deep constraints as the diamond net—short of suicide and de novo reinvention, short of obliterating themselves and constructing someone new. That meant that they had to possess their own immutable mathematical signatures—like the Euler number, only orders of magnitude more complex. Buried in the confusion of details of every mind, there had to be something untouched by time, unswayed by the shifting weight of memory and experience, unmodified by self-directed change.

Hashim’s artwork had been elegant and moving—and even without the outlook running, the powerful emotions it had evoked lingered—but Yatima was unswayed from vis choice of vocation. Art had its place, tweaking the remnants of all the instincts and drive, that the fleshers, in their innocence, had once mistaken for embodiments of immutable truth—but only in the Mines could ve hope to discover the real invariants of identity and consciousness.

Only in the Mines could ve begin to understand exactly who ve was.

3. Bridgers

Atlanta, Earth

23 387 545 324 947 CST

21 May 2975, 11:35:22.101 UT

Yatima’s clone started up in the gleisner body and spent a moment reflecting on vis situation. The experience of "awakening" felt no different from arriving in a new scape; there was nothing to betray the fact that vis whole mind had just been created anew. Between subjective instants, ve’d been cross-translated from Konishi’s dialect of Shaper, which ran on the virtual machine of a womb or an exoself, into the gleisner version which this robot’s highly un-polis-like hardware implemented directly. In a sense, ve had no past of vis own, just forged memories and a secondhand personality… but it still felt as if ve’d merely jumped from savanna to jungle, one and the same person before and after. All invariants intact.

The original Yatima had been suspended by vis exoself prior to translation, and if everything went according to plan that frozen snapshot would never need to be re-started. The Yatima-clone in the gleisner would be re-cloned back into Konishi polis (and re-translated back into Konishi Shaper), then both the Konishi original and the gleisner-bound clone would he erased. Philosophically, it wasn’t all that different from being shifted within the polis from one section of physical memory to another—an undetectable act which the operating system performed on every citizen from time to time, to reclaim fragmented memory space. And subjectively, the whole excursion would probably be much the same as if they’d puppeted the gleisners remotely, instead of literally inhabiting them.

If everything went according to plan.

Yatima looked around for Inoshiro. The sun had barely cleared the horizon, let alone penetrated the canopy, but the gleisner’s visual system still managed to deliver a crisp, high-contrast image. Thigh-high shrubs with huge, droopy, dark green lenticular leaves covered the forest floor nearby, between massive trunks of soaring hardwood. The interface software they’d cobbled together seemed to be working; the gleisner’s head and eyes tracked the angle-of-view bits of Yatima’s requests for data without any perceptible delay. Running eight hundred times slower than usual was apparently enough to let the machinery keep up—so long as ve remembered not to attempt any kind of discontinuous motion.

The other abandoned gleisner was sitting in the undergrowth beside ver, torso slumped forward, arms hanging limp. Its polymer skin was all but hidden, encrusted with dew-wet lichen and a thin layer of trapped soil. The mosquito-sized drone they’d used to port themselves into the gleisners' processors which had stumbled on the disused robots in the first place—was still perched on the back of the thing’s head, repairing the tiny incision it had made to gain access to a fiber trunkline.

"Inoshiro?" The linear word came hack at Yatima through the interface software, imprinted with all the strange resonances of the gleisner chassis, muffled at odd frequencies by the jungle’s clutter and humidity. No scape’s echo had ever been quite so… undesigned. So guileless. "Are you in there?"

The drone buzzed, and rose up from the sealed wound. The gleisner turned to face Yatima, dislodging wet sand and fragments of decaying leaves. Several large red ants, suddenly exposed, weaved confused figure-eights across the gleisner’s shoulder but managed to stay on.

"Yes, I’m here, don’t panic." Yatima began receiving the familiar signature, via an infrared link; ve instinctively challenged and confirmed it. Inoshiro flexed vis facial actuators experimentally, shearing off mulch and grime. Yatima played with vis own expression; the interface software kept sending back tags saying ve was attempting impossible deformations.

"If you want to stand up, I’ll brush some of that crap off you." Inoshiro rose smoothly to vis feet; Yatima willed vis viewpoint higher, and the interface made vis own robot body follow suit.

Ve let Inoshiro pummel and scrape ver, paying scant attention to the detailed stream of tags ve received describing the pressure changes on "vis" polymer skin. They’d arranged for the interface to feed the gleisners' posture, as reported by the hardware, into their own internal symbols for their icons—and to make the robots, in turn, obey changes to the icons (so long as they weren’t physically impossible, and wouldn’t send there sprawling to the ground)—but they’d decided against the kind of extensive re-design that would have given them deeply integrated flesher-style sensory feedback and motor instincts. Even Inoshiro had balked at the idea of their gleisner-clones gaining such vivid new senses and skills, only to slough them off upon returning to Konishi, where they would have been about as useless as Yatima’s object-sculpting talents were in this unobliging jungle. Having successive versions of themselves so dissimilar would have made the whole experience too much like death.

They swapped roles, Yatima doing vis best to brush Inoshiro clean. Ve understood all the relevant physical principles, and ve could cause the gleisner’s arms to do pretty much what ve liked by willing vis icon to make the right movements… but even with the interface to veto any actions which would have disrupted the elaborate balancing act of bipedal motion, it was blindingly obvious that the compromise they’d chosen left them clumsy beyond belief. Yatima recalled scenes from the library of fleshers involved in simple tasks: repairing machinery, preparing food, braiding each other’s hair. Gleisners were even more dextrous, when the right software was in charge. Konishi citizens retained the ancestral neural wiring for fine control of their icons' hands—linked to the language centers, for gestural purposes—but all the highly evolved systems for manipulating physical objects had been ditched as superfluous. Scape objects did as they were told, and even Yatima’s mathematical toys obeyed specialized constraints with only the faintest resemblance to the rules of the external world.

"What now?" Inoshiro just stood there for a moment, grinning diabolically. Vis robot body wasn’t all that different from vis usual pewter-skinned icon; the polymer beneath all the stains and lingering biota was a dull metallic gray, and the gleisner’s facial structure was flexible enough to manage a recognizable caricature of the real thing. Yatima still felt verself sending out the same lithe, purple-robed flesher icon as always; ve was almost glad ve couldn’t part vis navigators and clearly observe vis own drab physical appearance.

Inoshiro chanted, "Thirty-two kilotau. Thirty-three kilotau. Thirty-four kilotau."

"Shut up." Their exoselves back in Konishi had been instructed to explain to any callers precisely what they’d done no one would be left thinking that they’d simply turned catatonic—but Yatima still felt a painful surge of doubt. What would Blanca and Gabriel be thinking? And Radiya, and Inoshiro’s parents?

"You’re not backing out on me, are you?" Inoshiro eyed ver suspiciously.

"No!" Yatima laughed, exasperated; whatever vis misgivings, ve was committed to the whole crazy stunt. Inoshiro had argued that this was vis last chance to do anything "remotely exciting" before ve started using a miner’s outlook and "lost interest in everything else"—but that simply wasn’t true; the outlook was more like a spine than a straitjacket, a strengthened internal framework, not a constrictive cage. And ve’d kept on saying no until ve finally realized that Inoshiro was too stubborn to abandon vis plans, even when it turned out that not one of vis daring, radical Ashton-Laval friends was willing to accompany ver. Yatima had been secretly tempted all along by the idea of stepping right out of Konishi time and encountering the alien fleshers, though ve would have been just as happy to leave it all in the realms of plausible fantasy. In the end, it had come down to one question: If Inoshiro went ahead and did this alone, would it turn them into strangers? Yatima had found, to vis surprise, that this wasn’t a risk ve was willing to take.

Ve suggested hesitantly, "We might not want to stay for the full twenty-four hours, though." Eight-six megatau. "What if the whole place is empty, and there’s nothing to see?"

"It’s a flesher enclave. It won’t be empty."

"The last known contact was centuries ago. They could have died out, moved away… anything." Under an eight-hundred-year-old treaty, drones and satellites were not permitted to invade the privacy of the fleshers; the few dozen scattered urban enclaves where their own laws permitted them to clear away the wildlife completely and build concentrated settlements were supposed to be treated as inviolable. They had their own global communications network, but no gateways linked it to the Coalition; abuses on both sides dating back to the Introdus had forced the separation. Inoshiro had insisted that merely puppeting the gleisner bodies via satellite from Konishi would have been morally equivalent to sending in a drone—and certainly the satellites, programmed to obey the treaty, would not have permitted it—but inhabiting two autonomous robots who wandered in from the jungle for a visit was a different matter entirely.

Yatima looked around at the dense undergrowth, and resisted the futile urge to try to make vis viewpoint jump forward by a few hundred meters, or rise up into the towering forest for a better view of the terrain ahead. Fifty kilotau. Fifty-one. Fifty-two. No wonder most fleshers had stampeded into the polises, once they had the chance: if disease and aging weren’t reason enough, there was gravity, friction, and inertia. The physical world was one vast, tangled obstacle course of pointless, arbitrary restrictions.

"We’d better start moving."

"After You, Livingstone."

"Wrong continent, Inoshiro."

"Geronimo? Huckleberry? Dorothy?"

"Spare me."

They set off north, the drone buzzing behind them: their one link to the polis, offering the chance of a rapid escape if anything went wrong. It followed them for the first kilometer-and-a-half, all the way to the edge of the enclave. There was nothing to mark the border—just the same thick jungle on either side—but the drone refused to cross the imaginary line. Even if they’d built their own transceiver to take its place, it would have done them no good; the satellite footprints were shaped with precision to exclude the region. They could have rigged up a base station to re-broadcast from outside… but it was too late for that now.

Inoshiro said, "So what’s the worst thing that could happen?"

Yatima replied without hesitation. "Quicksand. We both fall into quicksand, so we can’t even communicate with each other. We just float beneath the surface until our power runs out." Ve checked vis gleisner’s energy store, a sliver of magnetically suspended anticobalt. "In six thousand and thirty-seven years."

"Or five thousand nine-hundred and twenty." Shafts of sunlight had begun to penetrate the forest; a flock of pink-and-gray birds were making rasping sounds in the branches above them.

"But our exoselves would restart our Konishi versions after two days—so we might as well commit suicide as soon as we’re sure we wouldn’t make it back by then."

Inoshiro regarded ver curiously. "Would you do that? I feel different from the Konishi version already. I’d want to go on living. And maybe someone would come along and pull us out in a couple of centuries."

Yatima thought it over. "I’d want to go on living—but not alone. Not without a single person to talk to."

Inoshiro was silent for a while, then ve held up vis right hand. Their polymer skins were dotted with IR transceivers all over, but the greatest density was on the palms. Yatima received a gestalt tag, a request for data. Inoshiro was asking for a snapshot of vis mind. The gleisner hardware was multiply redundant, with plenty of room for two.

Entrusting a version of verself to another citizen would have been unthinkable, back in Konishi. Yatima placed vis palm against Inoshiro’s, and they exchanged snapshots.

They crossed into the Atlanta enclave. Inoshiro said, "Update every hour?"

"Okay."

The interface software wasn’t too bad at walking. It kept them upright and steadily advancing, detecting obstacles in the ground cover and shifts in the terrain via the gleisners' tactile and balance senses, and whatever vision was available—without actually commandeering the head and eyes. After stumbling a few times, Yatima started glancing down every now and then, but it was soon clear how useful it would have been if the interface had been smart enough to plant an urge to do so in vis mind at appropriate times, like the original flesher instinct.

The jungle was visibly populated with small birds and snakes, but if there was any other animal life it was hiding or fleeing at the sound of them. Compared to walking through an indexscape for a comparable ecosystem, it was a rather dilute experience—and the thrill of interacting with real mud and real vegetation was beginning to wear thin.

Yatima heard something skid across the ground in front of ver; ve’d inadvertently kicked a small piece of corroded metal out from under a shrub. Ve kept walking, but Inoshiro paused to examine it, then cried out in alarm.

"What?"

"Replicator!"

Yatima turned back and angled for a better view; the interface made vis body crouch, "It’s just an empty canister." It was almost crushed flat, but there was still paint clinging to the metal in places, the colors faded to barely distinguishable grays. Yatima could make out a portion of a narrow, roughly longitudinal band of varying width, slightly paler than its background; it looked to ver like a two-dimensional representation of a twisted ribbon. There was also part of a circle-though if it was a biohazard warning, it didn’t look much like the ones ve recalled from vis limited browsing on the subject.

Inoshiro spoke in a hushed, sickened voice. "PreIntrodus, this was pandemic. Distorted whole nations' economies. It had hooks into everything: sexuality, tribalism, half a dozen artforms and subcultures… it parasitized the fleshers so thoroughly you had to he some kind of desert monk to escape it."

Yatima regarded the pathetic object dubiously, but they had no access to the library now, and vis knowledge of the era was patchy. "Even if there are traces left inside… I’m sure they’re all immune to it by now. And it could hardly infect us—"

Inoshiro cut ver off impatiently. "We’re not talking nucleotide viruses, here. The molecules themselves were just a random assortment of junk—mostly phosphoric acid; it was the memes they came wrapped in that made them virulent." Ve bent down lower, and cupped vis hands over the battered container. "And who knows how small a fragment it can bootstrap from? I’m not taking any chances." The gleisners' IR transceivers could be made to operate at high power; smoke and steam from singed vegetation rose up through Inoshiro’s fingers.

A voice came from behind them—a meaningless stream of phonemes, but the interface followed it with translation into linear: "Don’t tell me: you’re starting a fire to attract attention. You didn’t want to creep up on us unannounced."

They both turned as rapidly as their bodies permitted. The flesher stood a dozen meters away, dressed in a dark green robe shot through with threads of gold. Broadcasting no signature tag—of course, but Yatima still had to make a conscious effort to dismiss the instinctive conclusion that this was not a real person. Ve had black hair and eyes, copper-brown skin, and a thick black heard which in a flesher almost certainly meant gendered, male: ve was a he. No obvious modification: no wings, no gills, no photosynthetic cowl. Yatima resisted jumping to conclusions; none of this surface conservatism actually proved he was a static.

The flesher said, "I don’t think I’ll offer to shake hands." Inoshiro’s palms were still glowing dull red. "And we can’t exchange signatures. I’m at a loss for protocol. But that’s good. Ritual corrupts." He took a few steps forward; the undergrowth deferentially flattened itself to smooth his path. "I’m Orlando Venetti. Welcome to Atlanta."

They introduced themselves. The interface—pre-loaded with the most likely base languages, and enough flexibility to cope with drift had identified the flesher’s speech as a dialect of Modern Roman. It grafted the language into their minds, slipping new word sounds into all their symbols side-by-side with the linear versions, and binding alternative grammatical settings into their speech analysis and generation networks. Yatima felt distinctly stretched by the process—but vis symbols were still connected to each other in the same way as before. Ve was still verself.

"Konishi polis: Where is that, exactly?"

Yatima began to reply, "One hundred and— Inoshiro cut ver off with a burst of warning tags.

Orlando Was unperturbed. "Just idle curiosity; I wasn’t requesting coordinates for a missile strike. But what does it matter where you’ve come from, now that you’re here in the flesh? Or the gallium indium phosphide. I trust those bodies were empty when you found them?"

Inoshiro was scandalized. "Of course!"

"Good. The thought of real gleisners still prowling around on Earth is too horrible to contemplate. They should have come out of the factories with Born for Vacuum inscribed across their chests."

Yatima asked, "Were you born in Atlanta?"

Orlando nodded. "One hundred and sixty-three years ago. Atlanta fell empty in the 2600s-there was a community of statics here before, but disease wiped them out, and none of the other statics wanted to risk being infected. The new founders came from Turin, my grandparents among them." Ve frowned slightly. "So do you want to see the city? Or shall we stand here all day?"

With Orlando leading the way, obstacles vanished. However the plants were sensing his presence, they responded to it swiftly: leaves curling up, spines withdrawing like snails' stalks, sprawling shrubs contracting into tight cores, and whole protruding branches suddenly hanging limp. Yatima suspected that he was deliberately prolonging the effects to include them, and ve had no doubt that Orlando could have left any unwelcome pursuer far behind—or at least, anyone who lacked the same molecular keys.

Yatima asked, half jokingly, "Any quicksand around here?"

"Not if you stick close."

The forest ended without warning; if anything, the edge was more densely wooded than most of the interior, helping to conceal the transition. They emerged onto a vast, bright open plain, mostly taken up with fields of crops and photovoltaics. The city lay ahead in the distance: a broad cluster of low buildings, all vividly colored, with sweeping, geometrically precise curved walls and roofs intersecting and overlapping wildly.

Orlando said, "There are twelve thousand and ninety-three of us, now. But we’re still tweaking the crops, and our digestive symbionts; within ten years, we should be able to support four thousand more with the same resources," Yatima decided it would be impolite to inquire about their mortality rate. In most respects, the fleshers had a far harder time than the Coalition in trying to avoid cultural and genetic stagnation while eschewing the lunacy of exponential growth. Only true statics, and a few of the more conservative exuberants, retained the ancestral genes for programmed death and asking for a figure on accidental losses might have seemed insensitive.

Orlando laughed suddenly. "Ten years? What would that seem like to you? A century?"

Yatima replied, "About eight millennia."

"Fuck."

Inoshiro added hastily. "You can’t really convert, though. We might do a few simple things eight hundred times faster, but we change much more slowly than that."

"Empires don’t rise and fall in a year? New species don’t evolve in a century?"

Yatima reassured him, "Empires are impossible. And evolution requires vast amounts of mutation and death. We prefer to make small changes, rarely, and wait to see how they turn out."

"So do we." Orlando shook his head. "Still. Over eight thousand years, I have a feeling we won’t be keeping such a tight grip on things."

They continued on toward the city, following a broad path which looked like it was made of nothing more than reddish-brown clay, but probably teemed with organisms designed to keep it from eroding into dust or mud. The gleisner’s feet described the surface as soft but resilient, and they left no visible indentations. Birds were busy in the fields, eating weeds and insects—Yatima was only guessing, but if they were feeding on the crop itself the next harvest would be extremely sparse.

Orlando stopped to pick up a small leafy branch from the path, which must have blown in from the forest, then began sweeping it back and forth across the ground ahead of them. "So how do they greet dignitaries in the polises? Are you accustomed to having sixty thousand non-sentient slaves strewing rose petals at your feet?"

Yatima laughed, but Inoshiro was deeply offended. "We’re not dignitaries! We’re delinquents!"

As they drew nearer, Yatima could see people walking along the broad avenues between the rainbow-colored buildings—or loitering in groups, looking almost like citizens gathered in some forum, even if their appearance was much less diverse. Some had vis own icon’s dark skin, and there were other equally minor variations, but all of these exuberants could have passed for statics. Yatima wondered just what changes they were exploring; Orlando had mentioned digestive symbionts, but that hardly counted—it didn’t even involve their own DNA.

Orlando said, "When we noticed you coming, it was hard to decide who to send. We don’t get much news from the polises—we had no idea what you’d be like." He turned back to face them. "I do make sense to you, don’t I? I’m not just imagining that communication is taking place?"

"Not unless we’re imagining it, too." Yatima was puzzled. "What do you mean, though: who to send? Do some of you speak Coalition languages?"

"No." They’d reached the outskirts of the city; people were turning to watch them with undisguised curiosity. "I’ll explain soon. Or a friend of mine will."

The avenues were carpeted with thick, short grass. Yatima could see no vehicles or pack animals, just fleshers, mostly barefoot. Between the buildings there were flowerbeds, ponds and streams, statues still and moving, sundials and telescopes. Everything was space and light, open to the sky. There were parks, large enough for kite flying and ball games, and people sitting talking in the shade of small trees. The gleisner’s skin was sending tags describing the warmth of the sunlight and the texture of the grass; Yatima was almost beginning to regret not modifying verself enough to absorb the information instinctively.

Inoshiro asked, "What happened to pre-Introdus Atlanta? The skyscrapers? The factories? The apartment blocks?"

"Some of it’s still standing. Buried in the jungle, further north. I could take you there later, if you like."

Yatima got in quickly before Inoshiro could answer. "Thank you, but we won’t have time."

Orlando nodded at dozens of people, greeted some by name, and introduced Yatima and Inoshiro to a few. Yatima attempted to shake their offered hands, which turned out to be an extraordinarily complex dynamical problem. No one seemed hostile to their presence—hut Yatima found their gestalt gestures confusing, and no one uttered more than a few polite phrases before walking on.

"This is my home."

The building was pale blue, with an S-shaped facade and a smaller, elliptical second story. "Is this… some kind of stone?" Yatima stroked the wall and paid attention to the tags; the surface was smooth down to the sub-millimeter scale, but it was as soft and cool as the hark ve’d touched in the forest.

"No, it’s alive. Barely. It was sprouting twigs and leaves all over when it was growing, but now it’s only metabolizing enough for repairs, and a little active air conditioning." A strip-curtain covering the doorway parted for Orlando, and they followed him in. There were cushions and chairs, still pictures on the walls, dust-filled shafts of sunlight everywhere.

"Take a seat." They stared at him. "No? Fine. Could you wait here a second?" He strode up a staircase.

Inoshiro said numbly, "We’re really here. We did it." Ve surveyed the sunny room. "And this is how they live. It doesn’t look so bad."

"Except for the time scale."

Ve shrugged. "What are we racing, in the polises? We speed ourselves up as much as we can—then struggle not to let it change us."

Yatima was annoyed. "What’s wrong with that? There’s not much point to longevity if all you’re going to do with your time is change into someone else entirely. Or decay into no one at all."

Orlando returned, accompanied by a female flesher. "This is Liana Zabini. Inoshiro, and Yatima, of Konishi polis." Liana had brown hair and green eyes. They shook hands; Yatima was beginning to get the hang of doing it without either offering too much resistance, or merely letting vis arm hang limp. "Liana is our best neuroembryologist. Without her, the bridgers wouldn’t stand a chance."

Inoshiro said, "Who are the bridgers?"

Liana glanced at Orlando. He said, "You’d better start at the beginning." Orlando persuaded everyone to sit; Yatima finally realized that this was more comfortable for the fleshers.

Liana said, "We call ourselves bridgers. When the founders came here from Turin, three centuries ago, they had a very specific plan. You know there’ve been thousands of artificial genetic changes in different flesher populations, since the Introdus?" She gestured at a large picture behind her, and the portrait faded, to be replaced by a complex upside-down tree diagram. "Different exuberants have made modifications to all kinds of characteristics. Some have been simple, pragmatic adaptations for new diets or habitats: digestive, metabolic, respiratory, muscular-skeletal." Images flashed up from different points on the tree: amphibious, winged, and photosynthetic exuberants, close-ups of modified teeth, diagrams of altered metabolic pathways. Orlando rose from his seat and started drawing curtains; the contrast of the images improved.

"Often, habitat changes have also demanded neural modifications to provide appropriate new instincts; no one can thrive in the ocean, for example, without the right hardwired reflexes." A slick-skinned amphibious flesher rose slowly through emerald water, a faint stream of bubbles emerging from flaps behind vis ears; a transected, color-coded view showed dissolved gas concentrations in vis tissues and bloodstream, and an inset graph illustrated the safe range of staged ascents.

"Some neural changes have gone far beyond new instincts, though." The tree thinned-out considerably-but there were still thirty or forty current branches left. "There are species of exuberants who’ve changed aspects of language, perception, and cognition."

Inoshiro said, "Like the dream apes?"

Liana nodded. "At one extreme. Their ancestors stripped back the language centers to the level of the higher primates. They still have stronger general intelligence than any other primate, but their material culture has been reduced dramatically—and they can no longer modify themselves, even if they want to. I doubt that they even understand their own origins anymore.

"The dream apes are the exception, though—a deliberate renunciation of possibilities. Most exuberant, have tried more constructive changes: developing new ways of mapping the physical world into their minds, and adding specialized neural structures to handle the new categories. There are exuberants who can manipulate the most sophisticated, abstract concepts in genetics, meteorology, biochemistry, or ecology as intuitively as any static can think about a rock or a plant or an animal with the common sense about those things which comes from a few million years of evolution. And there are others who’ve simply modified ancestral neural structures to find out how that changes their thinking—who’ve headed out in search of new possibilities, with no specific goals in mind."

Yatima felt an eerie resonance with vis own situation… though from all the evidence so far, vis own mutations hadn’t exactly set him adrift in uncharted waters. As Inoshiro put it: "With you, they’ve finally stumbled on the trait fields for the ultimate in willing mine fodder. Parents will be asking for those nice compliant Yatima settings for the next ten gigatau."

Liana spread her arms in a gesture of frustration. "The only trouble with all this exploration is… some species of exuberants have changed so much that they can’t communicate with anyone else, anymore. Different groups have rushed off in their own directions, trying out new kinds of minds and now they can barely make sense of each other, even with software intermediaries. It’s not just a question of language—or at least, not the simple question that language was for the statics, when everyone had basically identical brains. Once different communities start carving up the world into different categories, and caring about wildly different things, it becomes impossible to have a global culture in anything like the pre-Introdus sense. We’re fragmenting. We’re losing each other." She laughed, as if to deflate her own seriousness, but Yatima could see that she was passionate about the subject. "We’ve all chosen to stay on Earth, we’ve all chosen to remain organic… but we’re still drifting apart probably faster than any of you in the polises!"

Orlando, standing behind her chair, placed a hand on her shoulder and squeezed it gently. She reached up and clasped her hand over his. Yatima found this mesmerizing, but tried not to stare. Ve said, "So how do the bridgers fit in?"

Orlando said, "We’re trying to plug the gaps."

Liana gestured at the tree diagram, and a second set of branches began to grow behind and between the first. The new tree was much more finely differentiated, with more branches, more closely spaced.

"Taking the ancestral neural structures as a starting point, we’ve been introducing small changes with every generation. But instead of modifying everyone in the same direction, our children are not only different from their parents, they’re increasingly different from each other. Each generation is more diverse than the one before."

Inoshiro said, "But… isn’t that the very thing you were lamenting? People drifting apart?"

"Not quite. Instead of whole populations jumping en masse to opposite ends of the spectrum for some neural trait giving rise to two distinct groups with no common ground—we’re always scattered evenly across the whole range. That way, no one is cut off, no one is alienated, because any given person’s 'circle'—the group of people with whom they can easily communicate—always overlaps with someone else’s, someone outside the first circle… whose own circle also overlaps with that of someone else again… until one way or another, everyone is covered.

"You could easily find two people here who can barely understand each other—because they’re as different as exuberants from two wildly divergent lines—but here, there’ll always be a chain of living relatives who can bridge the gap. With a few intermediaries—right now, four at the most—any bridger can communicate with any other."

Orlando added, "And once there are people among us who can interact with all of the scattered exuberant communities, on their own terms…"

"Then every flesher on the planet will be connected, in the same way."

Inoshiro asked eagerly, "So you could set up a chain of people who’d let us talk to someone at the edge of the process? Someone heading toward the most remote group of exuberants?"

Orlando and Liana exchanged glances, then Orlando said, "If you can wait a few days, that might be possible. It takes a certain amount of diplomacy; it’s not a party trick we can turn on at a moment’s notice."

"We’re going back tomorrow morning." Yatima didn’t dare look at Inoshiro; there’d be no end of excuses to extend their stay, but they’d agreed hours.

After a moment’s awkward silence, Inoshiro said calmly, "That’s right. Maybe next time."

Orlando showed them around the gene foundry where he worked, assembling DNA sequences and testing their effects. As well as their main goal, the bridgers were working on a number of non-neural enhancements involving disease resistance and improved tissue-repair mechanisms, which could be tried out with relative ease on brainless vegetative assemblies of mammalian organs which Orlando jokingly referred to as "offal trees." "You really can’t smell them? You don’t know how lucky you are."

The bridgers, he explained, had tailored themselves to the point where any individual could rewrite parts of vis own genome by injecting the new sequence into the bloodstream, bracketed by suitable primers for substitution enzymes, wrapped in a lipid capsule with surface proteins keyed to the appropriate cell types. If the precursors of gametes were targeted, the modification was made heritable. Female bridgers no longer generated all their ova while still fetuses, like statics did, but grew each one as required, and sperm and ova production—let alone the preparation of the womb for implantation of a fertilized egg—only occurred if the right hormones, available from specially-tailored plants, were ingested. About two-thirds of the bridgers were single-gendered; the rest were hermaphroditic or parthenogenetic—asexual, in the manner of certain species of exuberants.

After a tour of the facilities, Orlando declared that it was lunchtime, and they sat in a courtyard watching him eat. The other foundry workers gathered round; a few spoke to them directly, while the rest used intermediaries to translate. Their questions often came out sounding odd, even after some lengthy exchanges between translator and questioner—"How do you know which parts of the world are you, in the polises?" "Are there citizens in Konishi who eat music?" "Is not having a body like falling all the time, without moving?" and from the laughter their answers produced it was clear that the inverse process was just as imperfect. A certain amount of genuine communication did take place—but it depended heavily on trial and error, and a great deal of patience.

Orlando had promised to show them factories and silos, galleries and archives… but other people started dropping by to talk to them—or just to stare—and as the afternoon wore on, their original plans receded into fantasy. Perhaps they could have forced the pace, reminding their hosts how precious their time was, but after a few hours it began to seem absurd to have imagined that they could have done anything more, in a day. Nothing could be rushed, here; a whirlwind tour would have seemed like an act of violence. As the megatau evaporated, Yatima struggled not to think about the progress ve could have been making, back in the Truth Mines. Ve wasn’t racing anyone—and the Mines would still be there when ve returned.

Eventually the courtyard behind the foundry became so crowded that Orlando dragged everyone off to an outdoor restaurant. By dusk, when Liana joined them, the questions were finally beginning to dry up, and most of the crowd had split off into smaller groups who were busily discussing the visitors among themselves.

So the four of them sat and talked beneath the stars—which were dulled and heavily filtered by the narrow spectral window of the atmosphere. "Of course we’ve seen them from space," Inoshiro boasted. "In the polises, the orbital probes are just another address."

Orlando said, "I keep wanting to insist: Ah, but you haven’t seen them with your own eyes! Except… you have. In exactly the same way that you’ve seen anything at all."

Liana leaned on his shoulder and added teasingly, "Which is the same way anyone sees anything. Just because our own minds are being run a few centimeters away from our own cameras, that doesn’t make our experiences magically superior."

Orlando conceded, "No. This does, though."

They kissed. Yatima wondered if Blanca and Gabriel ever did that if Blanca had modified verself to make it possible, and pleasant. No wonder Blanca’s parents disapproved. Gabriel being gendered wasn’t such a big deal, as an abstract question of self-definition—but almost everyone in Carter-Zimmerman also pretended to have a tangible body. In Konishi, the whole idea of solidity, of atavistic delusions of corporeality, was generally equated with obstruction and coercion. Once your icon could so much as block another’s path in a public scape, autonomy was violated. Re-connecting the pleasures of love to concepts like force and friction was simply barbaric.

Liana asked, "What are the gleisners up to? Do you know? Last we heard, they were doing something in the asteroid belt—but that was almost a hundred years ago. Have any of them left the solar system?"

Inoshiro said, "Not in person. They’ve sent probes to a few nearby stars, but nothing sentient yet—and when they do, it will be them-in-their-whole-bodies, all the way." Ve laughed. "They’re obsessed with not becoming polis citizens. They think if they dare take their heads off their shoulders to save a bit of mass, next thing they’ll he abandoning reality entirely."

Orlando said contemptuously, "Give them another thousand years, and they’ll he pissing up and down the Milky Way, marking their territory like dogs."

Yatima protested, "That’s not fair! They might have bizarre priorities… but they’re still civilized. More or less."

Liana said, "Better gleisners out there than fleshers. Can you imagine statics in space? They’d probably have terraformed Mars by now. The gleisners have barely touched the planet; mostly they’ve just surveyed it from orbit. They’re not vandals. They’re not colonists."

Orlando was unconvinced. "If all you want to do is gather astrophysical data, there’s no need to leave the solar system. I’ve seen plans: seeding whole worlds with self-replicating factories, filling the galaxy with Von Neumann machines—"

Liana shook her head. "If that sort of thing was ever meant seriously, it was pre-Introdus—before gleisners even existed. Anything contemporary is just propaganda: Protocols of the Elders of Machinehood stuff. We’re the ones still closest to the old drives. If anyone screws up and goes exponential, it will probably be us."

Some other bridgers joined in, and the debate dragged on for hours. One agronomist argued, through an interpreter: If space travel wasn’t just a fantasy for immature cultures, then where were all the aliens? Yatima glanced up at the drab sky every now and then, and imagined a gleisner spacecraft swooping down and carrying them off to the stars. Maybe some rescue beacon had started up in the gleisner bodies when they’d reactivated them… It was an absurd notion, but it was strange to ponder the fact that it wasn’t literally impossible. Even in the most dazzling astronomical scape, where you could pretend to jump across the light years and see the surface of Sirius in the best high-resolution composite of simulation and telescope-based data… you could never be kidnapped by mad astronauts.

Just after midnight, Orlando asked Liana, "So who’s getting up at four in the morning to escort our guests to the border?"

"You are."

"Then I’d better get some sleep."

Inoshiro was amazed. "You still have to do that? You haven’t engineered it out?"

Liana made a choking sound. "That’d be like engineering-out the liver! Sleep’s integral to mammalian physiology; try taking it away, and you’d end up with psychotic, immune-compromised cretins."

Orlando added grumpily, "It’s also very nice. You don’t know what you’re missing." He kissed Liana again, and left them.

The crowd in the restaurant thinned out slowly—and then most of the bridgers who remained fell asleep in their chairs—but Liana sat with them in the growing silence.

"I’m glad you came," she said. "Now we have some kind of bridge to Konishi—and through you, to the whole Coalition. Even if you can’t return… talk about us, inside. Don’t let us vanish from your minds completely."

Inoshiro said earnestly, "We’ll come hack! And we’ll bring our friends. Once they understand that you’re not all savages out here, everyone will want to visit you."

Liana laughed gently. "Yeah? And the Introdus will run backward, and the dead will rise from their graves? I’ll look forward to that." She reached across the table and brushed Inoshiro’s cheek with her hand. "You’re a strange child. I’m going to miss you."

Yatima waited for Inoshiro’s outraged response: I am not a child. But instead, ve put vis hand to vis face, where she’d touched ver, and said nothing.

Orlando escorted them all the way to the border. He bid them farewell, and talked about seeing them again, but Yatima suspected that he, too, didn’t believe they’d ever return. When he’d vanished into the jungle, Yatima stepped over the border and summoned the drone. It alighted on the back of vis neck, and burrowed in to make contact with vis processor. The gleisner’s neck, the gleisner’s processor.

Inoshiro said, "You go. I’m staying."

Yatima groaned. "You don’t mean that."

Inoshiro stared back at ver, forlorn but resolute. "I was born in the wrong place. This is where I belong."

"Oh, get serious! If you want to migrate, there’s always Ashton-Laval! And if you want to escape your parents, you can do that anywhere!"

Inoshiro sat down in the undergrowth, vanishing up to vis waist, and spread vis arms out in the foliage. "I’ve started feeling things. It’s not just tags anymore—not lust an abstract overlay." Ve brought vis hands together against vis chest, then thumped the chassis. "It happens to me, it happens on my skin. I must have formed some kind of map of the data… and now my self symbol’s absorbed it, incorporated it." Ve laughed miserably. "Maybe it’s a family weakness. My part-sibling takes an embodied lover… and now here I am, with a fucking sense of touch." Ve looked up at Yatima, eyes wide, gestalt for horror. "I can’t go back now. It’d be like… tearing off my skin."

Yatima said flatly, "You know that’s not true. What do you think’s going to happen to you? Pain? As soon as the tags stop coming, the whole illusion will dissolve." Ve was trying to be reassuring, but ve struggled to imagine what it must be like: some kind of intrusion of the world into Inoshiro’s icon? It was confusing enough when the interface adjusted vis own icon’s symbol to the actual posture of vis gleisner body—but that was more like playing along with the conventions of a game; there was no deep sense of violation…

Inoshiro said, "They’ll let me live with them. I don’t need food, I don’t need anything they value. I’ll make myself useful. They’ll let me stay."

Yatima stepped back over the border; the drone broke free and retreated, buzzing angrily. Ve knelt down beside Inoshiro and said gently, "Tell the truth: you’d go mad within a week. One scape, like this, forever? And once the novelty wore off, they’d treat you like a freak."

"Not Liana!"

"Yeah? What do you think she’d become? Your lover? Or yet another parent?"

Inoshiro covered vis face with vis hands. "Just crawl back to Konishi, will you? Go lose yourself in the Mines."

Yatima stayed where ve was. Birds squawked, the sky brightened. Their twenty-four hours expired. They still had one more day before their old Konishi-selves awoke in their place-but with each passing minute, now, the sense of polis life moving on and leaving them behind grew stronger.

Yatima thought of dragging Inoshiro over the line, and instructing the drone to pluck ver from vis bode. The drone wasn’t smart enough to understand anything they’d done; it wouldn’t realize it was violating Inoshiro’s autonomy.

And that idea was disturbing enough, but there was another possibility. Yatima still had the last updated snapshot of Inoshiro’s mind, transmitted in the restaurant in the early hours of the morning. Inoshiro wouldn’t have sent it after ve’d made up vis mind to stay—and it Yatima woke that snapshot inside the polis, it wouldn’t matter what happened to this gleisner-clone…

Yatima erased the snapshot. This wasn’t quicksand. This wasn’t anything they’d foreseen.

Ve knelt, and waited. The tags from vis knees reporting the texture of the ground became an irritating, monotonous stream, and the strange fixed shape forced upon vis icon grew even more annoying—perhaps because they both mirrored vis frustration so well. Was this how it had started, for Inoshiro? If ve stayed here much longer, would ve begin to identify with vis own map of vis own gleisner body?

After almost an hour, Inoshiro rose to vis feet and walked out of the enclave. Yatima followed ver, sick with relief.

The drone landed on Inoshiro’s neck; ve reached up as if to slap it away, but stopped verself. Ve asked calmly, "Do you think we’ll ever come back?" Yatima thought about it, long and hard. Without the unrepeatable allure which had brought them here, would this place, and these friends, ever again be worth eight hundred times more than all the rest?

"I doubt it."

Part Two

When Paolo woke and joined ver in the scape, Yatima said, "I’m trying to decide what we should tell them. When they ask why we came after them."

Paolo laughed grimly. "Tell them about Lacerta."

"They’ll know about Lacerta."

"As a blip on a map. They won’t know what it did. They won’t know what it meant."

"No." Yatima gazed at Weyl, at the center of the blue shift. Ve didn’t want to antagonize Paolo with questions about Atlanta, but ve didn’t want to shut him out either. "You know Karpal, don’t you?"

"Yes." Paolo accepted the present tense with a faint smile.

"And wasn’t he on the moon, running TERAGO "

Paolo said coldly, "He did everything he could. It wasn’t his fault the whole planet was sleepwalking."

"I agree. I don’t blame him for anything." Yatima spread vis arms, conciliatory. "I just wondered if he’d ever talked about it. If he ever told you his side of things."

Paolo nodded grudgingly. "He talked about it. Once."

4. Lizard heart

Bullialdus observatory, Moon

24 046 104 526 757 CST

2 April 2996, 16:42:03.911 UT

Karpal lay on his back on the regolith for a full lunar month, staring up into the crystalline stillness of the universe and daring it to show him something new. He’d done this five times before, but nothing had ever changed within reach of his unaided vision. The planets moved along their predictable orbits, and sometimes a bright asteroid or comet was visible, but they were like spacecraft wandering by: obstacles in the foreground, not part of the view. Once you’d seen Jupiter close-up, firsthand, you began to think of it more as a source of light pollution and electromagnetic noise than as an object of serious astronomical interest. Karpal wanted a supernova to blossom out of the darkness unforeseen, a distant apocalypse to set the neutrino detectors screaming—not some placid conjunction of the solar system’s clockwork, as noteworthy and exciting as a supply shuttle arriving on time.

When the Earth was new again, a dim reddish disk beside the blazing sun, Karpal rose to his feet and swung his arms cautiously, checking that none of his actuators had been weakened by thermal stress. If they had, it wouldn’t take long for his nanoware to smooth away the microfractures, but each joint still needed to be tested by use in order to notice the problem and call for repairs.

He was fine. He walked slowly hack to the instrumentation shack at the edge of Bullialdus crater; the structure was open to the vacuum, but it sheltered the equipment to some degree from temperature extremes, hard radiation and micrometeorites. Looming behind it was the crater wall, seventy kilometers wide; Karpal could just make out the laser station on top of the wall, directly above the shack. The beams themselves were invisible from any vantage, since there was nothing to scatter the light, but Karpal couldn’t picture Bullialdus from above without mentally inscribing a blue L, a right-angle linking three points on the rim.

Bullialdus was a gravitational wave detector, part of a solar-system-wide observatory known as TERAGO. A single laser beam was split, sent along perpendicular journeys, then recombined; as the space around the crater was stretched and squeezed by as little as one part in ten-to-the-twenty-fourth, the crests and troughs of the two streams of light were shifted in and out of alignment, causing fluctuations in their combined intensity which tracked the subtle changes of geometry. One detector, alone, could no more pinpoint the source of the distortions it measured than a thermometer lying on the regolith could gauge the exact position of the sun, but by combining the timing of events at Bullialdus with data from the nineteen other TERAGO sites, it was possible to reconstruct each wavefront’s passage through the solar system, revealing its direction with enough precision, usually, to match it to a known object in the sky, or at least make an educated guess.

Karpal entered the shack, his home for the last nine years. Nothing had changed in his absence, and little had changed since his arrival; the racks of optical computers and signal processors lining the walls looked as gleamingly pristine as ever, and his emergency spares kit and macro repair tools had barely been moved from where he’d first placed them. He wasn’t quite alone on the moon—there were a dozen gleisners doing paleoselenology up at the north pole—but he was yet to receive a visitor.

Almost every other gleisner was in the asteroid belt, either working on the interstellar fleet, providing some kind of support service, or generally playing camp follower. He could have been there himself, in the thick of it—the TERAGO data was accessible anywhere, and being physically present at one site offered few advantages when overseeing repairs for all twenty—but he’d been tempted by the solitude here, and the chance to work without distractions, devoting himself to a single problem for a week, or a month, or a year. Lying on the regolith gazing up at the sky for a month at a time hadn’t been in his original plans, but he’d always expected to go slightly crazy, and this seemed like a mild enough eccentricity. At first, he’d been afraid of missing an important event: a supernova, or a distant galactic core’s black hole swallowing a globular cluster or two. Every speck of data was logged, of course, but even when the gravitational waves had taken millennia to arrive there was a certain thrill of immediacy about monitoring them in real time; to Karpal, now was a transect of space-time ten billion years deep, converging on his instruments and senses at the speed of light.

Later, the risk of being away from his post became part of the attraction. Part of the dare.

Karpal checked the main display screen, and laughed softly in pulse-coded infrared; the faint heat echoed back at him from the walls of the shack. He’d missed nothing. On the list of known sources, Lac G-1 was highlighted as showing an anomaly but it was always showing anomalies; this no longer qualified as news.

As well as recording any sudden catastrophes, TERAGO was constantly monitoring a few hundred periodic sources. It took an event of rare violence to produce a burst of gravitational radiation sufficiently intense to be picked up halfway across the universe, but even routine orbital motion created a weak but dependable stream of gravitational waves. If the objects involved were as massive as stars, orbited each other rapidly, and weren’t too remote, TERAGO could tune into their motion like a hydrophone eavesdropping on a churning propeller.

Lacerta G-1 was a pair of neutron stars, a mere hundred light years away. Though neutron stars were far too small to be observed directly—about twenty kilometers wide, at most—they packed the magnetic and gravitational fields of a full-sized star into that tiny volume, and the effects on any surrounding matter could be spectacular. Most were discovered as pulsars, their spinning magnetic fields creating a rotating beam of radio waves by dragging charged particles around in circles at close to lightspeed, or as X-ray sources, siphoning material from a gas cloud or a normal companion star and heating it millions of degrees by compression and shock waves on its way down their tight, steep gravity well. Lac G-1 was billions of years old, though; any local reservoir of gas or dust which might have been used to make X-rays was long gone, and any radio emissions had either grown too weak to detect, or were being beamed in unfavorable directions. So the system was quiet across the electromagnetic spectrum, and it was only the gravitational radiation from the dead stars' slowly decaying orbit that betrayed their existence.

This tranquillity wouldn’t last forever. G-1a and G-1b were separated by just half a million kilometers, and over the next seven million years gravitational waves would carry away all the angular momentum that kept them apart. When they finally collided, most of their kinetic energy would be converted into an intense flash of neutrinos, faintly tinged with gamma rays, before they merged to form a black hole. At a distance, the neutrinos would be relatively harmless and the "tinge" would carry a far greater sting; even a hundred light years would he uncomfortably close, for organic life. Whether or not the fleshers were still around when it happened, Karpal liked to think that someone would take on the daunting engineering challenge of protecting the Earth’s biosphere, by placing a sufficiently large and opaque shield in the path of the gamma ray burst. Now there was a good use for Jupiter. It wouldn’t he an easy task, though; Lac G-1 was too far above the ecliptic to be masked by merely nudging either planet into a convenient point on its current orbit.

Lac G-1’s fate seemed unavoidable, and the signal reaching TERAGO certainly confirmed the orbit’s gradual decay. One small puzzle remained, though: from the first observations, G-la and G-1b had intermittently spiraled together slightly faster than they should have. The discrepancies had never exceeded one part in a thousand—the waves quickening by an extra nanosecond over a couple of days, every now and then—but when most binary pulsars had orbital decay curves perfect down to the limits of measurement, even nanosecond glitches couldn’t be written off as experimental error or meaningless noise.

Karpal had imagined that this mystery would be among the first to yield to his solitude and dedication, but a plausible explanation had eluded him, year after year. Any sufficiently massive third body, occasionally perturbing the orbit, should have added its own unmistakable signature to the gravitational radiation. Small gas clouds drifting into the system, giving the neutron stars something they could pump into energy-wasting jets, should have caused Lac G-1 to blaze with X-rays. His models had grown wilder and more daring, but all of them had come unstuck from a lack of corroborative evidence, or from sheer implausibility. Energy and momentum couldn’t just be disappearing into the vacuum, but by now he was almost ready to give up trying to balance the books from a hundred light years away.

Almost. With a martyr’s sigh, Karpal touched the highlighted name on the screen, and a plot of the waves from Lacerta for the preceding month appeared.

It was clear at a glance that something was wrong with TERAGO. The hundreds of waves on the screen should have been identical, their peaks at exactly the same height, the signal returning like clockwork to the same maximum strength at the same point on the orbit. Instead, there was a smooth increase in the height of the peaks over the second half of the month—which meant that TERAGO’s calibration must have started drifting. Karpal groaned, and flipped to another periodic source, a binary pulsar in Aquila. There were alternating weak and strong peaks here, since the orbit was highly elliptical, but each set of peaks remained perfectly level. He checked the data for five other sources. There was no sign of calibration drift for any of them.

Baffled, Karpal returned to the Lac G-1 data. He examined the summary above the plot, and sputtered with disbelief. In his absence, the summary claimed, the period of the waves had fallen by almost three minutes. That was ludicrous. Over 28 days, Lac G-1 should have shaved 14.498 microseconds off its hour-long orbit, give or take a few unexplained nanoseconds. There had to he an error in the analysis software; it must have become corrupted, radiation-damaged, a few random bits scrambled by cosmic rays somehow avoiding detection and repair.

He flipped to a plot showing the period of the waves, rather than the waves themselves. It began as it should have, virtually flat at 3627 seconds, then about 12 days into the data set it began to creep down from the horizontal, slowly at first, but at an ever-increasing rate. The last point on the curve was at 3456 seconds. The only way the neutron stars could have moved into a smaller, faster orbit was by losing some of the energy that kept them apart—and to be three minutes faster, instead of 14 microseconds, they would have needed to lose about as much energy in a month as they had in the past million years.

"Bollocks."

Karpal checked for news from other observatories, but there’d been no activity detected in Lacerta: no X-rays, no UV, no neutrinos, nothing. Lac G-1 had supposedly just shed the energy equivalent of the moon annihilating its antimatter double; even a hundred light years away, that could hardly have passed unnoticed. The missing energy certainly hadn’t gone into gravitational radiation; the apparent power increase there was just 17 percent.

And the period had fallen about 5 percent. Karpal did some calculations in his head, then had the analysis software confirm them in detail. The increasing strength of the gravitational waves was exactly what their decreasing period required. Closer, faster orbits produced stronger gravitational radiation, and this impossible data agreed with the formula, every step of the way. Karpal could not imagine a software error or calibration failure that could mangle the data for one source only while magically preserving the correct physical relationship between the power and frequency of the waves.

The signal had to he genuine.

Which meant the energy loss was real.

What was happening out there? Or had happened, a century ago? Karpal looked down a column of figures showing the separation between the neutron stars, as deduced from their orbital period. They’d been moving together steadily at about 48 millimeters a day since observations began. In the preceding twenty-four hours, though, the distance between them had plummeted by over 7,000 kilometers.

Karpal suffered a moment of pure vertiginous panic, but then quickly laughed it off. Such a spectacularly alarming rate of descent couldn’t be sustained for long. Apart from gravitational radiation, there were only two ways to steal energy from a massive cosmic flywheel like this: frictional loss to gas or dust, giving rise to truly astronomical temperatures—ruled out by the absence of UV and X-rays—or the gravitational transfer of energy to another system: some kind of invisible interloper, like a small black hole passing by. But anything capable of absorbing more than a fraction of G-1’s angular momentum would have shown up on TERAGO by now, and anything less substantial would soon he swept away, like a pebble skipping off a grindstone, or blown apart like an exploding centrifuge.

Karpal had the software analyze the latest data from TERAGO’s six nearest detectors, instead of waiting an hour for the full set to arrive. There was still no evidence of any kind of interloper—just the classical signature of a two-body system—but the energy loss showed no sign of halting, or even leveling off.

It was still growing stronger.

How? Karpal suddenly recalled an old idea which he’d briefly considered as an explanation for the minor anomalies. Individual neutrons were always color neutral: they contained one red, one green and one blue quark, tightly bound. But if both cores had "melted" into pools of unconfined quarks able to move about at random, their color would not necessarily average out to neutrality everywhere. Kozuch Theory allowed the perfect symmetry between red, green, and blue quarks to be broken; this was normally an extremely fleeting occurrence, but it was possible that interactions between the neutron stars could stabilize it. Quarks of a certain color could become "locally heavier" in one core, causing them to sink slightly until the attraction of the other quarks buoyed them up; in the other core, quarks of the same color would be lighter, and would rise. Tidal and rotational forces would also come into play.

The separation of color would be minute, but the effects would be dramatic: the two orbiting, polarized cores would generate powerful jets of mesons, which would act to brake the neutron stars' orbital motion a kind of nuclear analogue of gravitational radiation, but mediated by the strong force and hence much more energetic. The mesons would decay almost at once into other particles, but this secondary radiation would be very tightly focused, and since the view from the solar system was high above the plane of Lac G-1’s orbit the beams would never be seen head-on. No doubt they’d become spectacularly visible once they slammed into the interstellar medium, but after only 16 days they’d still he traveling through the region of relatively high vacuum that the neutron stars had swept clean over the last few billion years.

The whole system would be like a giant Catherine wheel in reverse, with the fireworks pointing backward, opposing their own spin. But as they bled away the angular momentum that kept them apart, gravity would draw them tighter and they’d whip around faster. The nanosecond glitches in the past might have involved small pools of mobile quarks forming briefly, then freezing back into distinct neutrons again, but once the cores melted completely it would be a runaway process: the closer the neutron stars came to each other, the greater their polarization, the stronger the jets, the more rapid their inward spiral.

Karpal knew that the calculations needed to test this idea would be horrendous. Dealing with interactions between the strong force and gravity could bring the most powerful computer to its knees, and any software model accurate enough to he trusted would run far slower than real time, making it useless for predictions. The only way to anticipate the fate of Lac G-1 was to try to see where the data itself was heading.

He had the analysis software fit a smooth curve through the neutron stars' declining angular momentum, and extrapolate it into the future. The fall grew faster, gently at first, but it ended in a steep descent. Karpal felt a cool horror wash through him: if this was the ultimate fate of every binary neutron star, it helped make sense of an ancient puzzle. But it was not good news.

For centuries, astronomers had been observing powerful gamma-ray bursts from distant galaxies. If these bursts were due to colliding neutron stars, as suspected, then just before the collision—when the neutron stars were in their closest, fastest orbits—the gravitational waves produced should have been strong enough for TERAGO to pick up over a range of billions of light years. No such waves had ever been detected.

But now it looked as though Lac G-1’s meson jets would succeed in bringing the neutron stars' orbital motion to a dead halt while they were still tens of thousands of kilometers apart. The Catherine wheel’s fireworks, having finally triumphed, would sputter out, and the end wouldn’t be a frenzied spiral after all, but a calm, graceful dive—generating only a fraction as much gravitational radiation.

Then the two mountain-sized star-heavy nuclei would slam straight together, as if there’d never been a hint of centrifugal force to keep them apart. They’d fall right out of each other’s sky—and the heat of the impact would be felt for a thousand light years. Karpal dismissed the image angrily. So far, he had nothing but a three-minute anomaly in an orbital period, and a lot of speculation. What was his judgment worth, after nine years of solitude and far too many cosmic rays? He had to get in touch with colleagues in the asteroid belt, show them the data, and talk through the possibilities calmly.

But if he was right? How long did the fleshers have before Lacerta lit up with gamma rays, six thousand times brighter than the sun?

Karpal checked and re-checked the calculations, fitted curves to different variables, tried every known method of extrapolation.

The answer was the same every time.

Four days.

5. Burster

Konishi polis, Earth

24 046 380 271 801 CST

5 April 2996,21:17:48.955 UT

Yatima floated in the sky above vis homescape, surveying the colossal network that sprawled across the hidden ground as far as ve could see. The structure was ten thousand delta wide and seven thousand high; winding around it was a single, elaborate curve, which looked a bit like one of the roller coaster rides ve’d seen in Carter-Zimmerman—and which ve’d ridden with Blanca and Gabriel, for the visual thrill alone. The "track" here was unsupported, just like the one in C-Z, but it weaved its way through what looked like a riot of scaffolding.

Yatima descended for a closer inspection. The network, the "scaffolding," was a piece of vis mind, based on a series of snapshots ve’d taken a few megatau before. The space around it glowed softly in a multitude of colors, imbued with an abstract mathematical field, a rule for taking a vector at any point and calculating a number from it, generated by the billions of pulses traveling along the network’s pathways. The curve that wrapped the network encircled every pathway, and by summing the numbers that the field produced from the tangents to the curve along its entire length, Yatima was hoping to measure some subtle but robust properties of the way information flowed through the structure.

It was one more tiny step toward finding an invariant of consciousness: an objective measure of exactly what it was that stayed the same between successive mental states, allowing an ever-changing mind to feel like a single, cohesive entity. The general idea was old, and obvious: short-term memories had to make sense, accumulating smoothly from perceptions and thoughts, then either fading into oblivion or drifting into long-term storage. Formalizing this criterion was difficult, though. A random sequence of mental states wouldn’t feel like anything at all, but neither would many kinds of highly ordered, strongly correlated patterns. Information had to flow in just the right way, each perceptual input and internal feedback gently imprinting itself on the network’s previous state.

When Inoshiro called, Yatima didn’t hesitate to let ver into the scape; it had been far too long since they’d last met. But ve was bemused by the icon that appeared in the air beside ver: Inoshiro’s pewter surface was furrowed and pitted, discolored with corrosion and almost flaking away in places; if not for the signature, Yatima would barely have recognized ver. Ve found the affectation comical, but kept silent; Inoshiro usually viewed the fads to which ve subscribed with appropriate irony, but occasionally ve turned out to be painfully earnest. Yatima had been persona non grata for almost a gigatau after mocking the practice, briefly fashionable across the Coalition, of carrying around a framed portrait of one’s icon "aging" in fast-motion.

Inoshiro said, "What do you know about neutron stars?"

"Not a lot. Why?"

"Gamma-ray bursters?"

"Even less." Inoshiro looked serious underneath all the rust, so Yatima struggled to remember the details from vis brief flirtation with astrophysics. "I know that gamma rays have been detected from millions of ordinary galaxies—one-off flashes, rarely from the same place twice. The statistics come down to something like one per galaxy per hundred thousand years… so if they weren’t bright enough to be seen a few billion light years away, we probably wouldn’t even know about them yet. I don’t think the mechanism’s been conclusively established, but I could check in the library—"

"There’s no point; it’s all out-of-date. Something’s happening, outside."

Yatima listened to the news from the gleisners, not quite believing it, staring past Inoshiro into the scape’s empty sky. Oceans of quarks, invisible meson jets, plummeting neutron stars… it all sounded terribly quaint and arcane, like some elegant but over-specific theorem at the end of a cul-de-sac.

Inoshiro said bitterly, "The gleisners took forever to convince themselves that the effect was real. We’ve got less than twenty-four hours before the burst hits. A group in Carter-Zimmerman is trying to break into the fleshers' communications network, but the cable is sheathed with nanoware, it’s defending itself too well. They’re also working on reshaping the satellite foot prints, and sending drones straight into the enclaves, but so far—"

Yatima cut in. "I don’t understand. How can the fleshers be in any kind of danger? They might not he as heavily shielded as we are, but they still have the whole atmosphere above them! What portion of the gamma rays will make it to ground level?"

"Almost none. But almost all of them will make it to the lower stratosphere." An atmospheric specialist in C-Z had modeled the effects in detail; Inoshiro offered an address tag, and Yatima skimmed the file.

The ozone layer over half the planet would be destroyed, immediately. Nitrogen and oxygen in the stratosphere, ionized by the gamma rays, would combine into two hundred billion tons of nitric oxides, thirty thousand times the current amount. This shroud of NOx would not only lower surface temperatures by several degrees, it would keep the ultraviolet window open for a century, catalyzing the destruction of ozone as fast as it reformed. Eventually, the nitric oxide molecules would drift into the lower atmosphere, where some would split apart into their harmless constituents. The rest—a few billion tons—would fall as acid rain.

Inoshiro continued grimly, "Those predictions all assume a certain total energy for the gamma-ray burst, but that could be as wrong as everything else people thought they knew about Lacerta G-1. At best, the fleshers will need to redesign their whole food supply. At worst, the biosphere could be crippled to the point where it can’t support them at all."

"That’s terrible." But Yatima felt verself retreating into a kind of weary resignation. Some fleshers would almost certainly die… but then, fleshers had always died. They’d had centuries to come into the polises if they’d wanted to leave the precarious hospitality of the physical world behind. Ve glanced down at vis glorious experiment; Inoshiro still hadn’t even given ver a chance to mention it.

"We have to warn them. We have to go back."

"Go back?" Yatima stared at ver, baffled.

"You and I. We have to go back to Atlanta."

A tentative image appeared: two fleshers, one of them seated. A man and a woman? Yatima had a feeling ve’d seen them in some artwork of Inoshiro’s, long ago. We have to go back to Atlanta? Was that a line from the same piece? Inoshiro’s slogans all began to sound the same after a while: "We must all go and work in our gardens," "We have to go back to Atlanta"…

Yatima consciously invoked full retrieval of the fragment’s context. As ve’d aged, ve’d opted for memory layering—rather than degradation or outright erasure—to keep vis thoughts from being swamped with a paralyzing excess of recollections. They’d taken two abandoned gleisners for a ride! Just the two of them, when Yatima was barely half a gigatau old. They’d been gone for something like eighty megatau-which must have seemed like an eternity at that age, though as it turned out even Inoshiro’s parents had been unfazed by the whole juvenile stunt. The jungle. The city surrounded by fields. They’d been afraid of quicksand—but they’d found a guide.

For a moment, Yatima was too ashamed to speak. Then ve said numbly, "I’d buried them. Orlando, Liana… the bridgers. I’d buried them all." Over time, ve’d let the whole experience sink from layer to layer to make room for more current preoccupations—until it could no longer enter vis thoughts by chance at all, interact with other memories, sway vis attitudes and moods. Until fleshers were just fleshers again: anonymous and remote, exotic and dispensable. The apocalypse could have come and gone, and ve would have done nothing.

Inoshiro said, "There isn’t much time. Are you with me, or not?"

Atlanta, Earth

24 046 380 407 629 CST

5 April 2996, 21:20:04.783 UT

The gleisners were exactly where they’d left them, twenty-one years before. Once they were awake, they each had the drone pass them a file of instructions for the robots' maintenance nanoware. Yatima watched nervously as the programmable sludge flowing in fine tubes throughout vis body began reconstructing the tip of vis right index finger into something alarmingly like a projectile weapon.

That was the easy part. When the delivery system was completed, the maintenance nanoware’s small subpopulation of assemblers was instructed to begin manufacturing Introdus nanoware. Yatima had been worried that the gleisners' assemblers, never designed for such demanding work, might not be capable of meeting the necessary tolerances, but the Introdus system’s self-testing procedure returned an encouraging report: less than one atom in ten-to-the-twentieth incorrectly bonded. Working on feedstock in the gleisner, the assemblers managed to build three hundred and ninety-six doses; if more were needed, the bridgers would probably be able to supply the necessary raw materials. There were well-stocked portals scattered across the planet where any flesher who wished to enter the Coalition could do so, but it had always been judged politically insensitive to place them too close to the enclaves. The nearest one to Atlanta was over a thousand kilometers away.

Inoshiro used vis own gleisner’s nanoware to build a pair of relay drones to keep them in touch with Konishi: no one had yet been able to trick the satellites into reshaping their footprints to include the enclaves. Yatima watched the glistening insectile machines forming in a translucent cyst on Inoshiro’s forearm, then burrow out and disappear into the canopy. They’d based the design on existing drones, but these bootleg versions were entirely unfettered by prior instructions and treaty obligations, and would shamelessly fool the satellites into accepting a signal re-routed from within the forbidden region.

They stepped across the border. To test their link to the Coalition, Yatima glanced at a C-Z scape based on a feed from TERAGO. Two dark spheres limned by gravitationally-lensed starlight moved through a faintly sketched spiral tube, the tight record of past orbits widening out into the uncertainty of extrapolation; the hypothetical meson jets were omitted altogether. The neutron stars broadcast gestalt tags with their current orbital parameters, while points on the spiral at regular intervals offered past and future versions.

The orbit had shrunk by a "mere" 20 percent so far—100,000 kilometers—but the process was highly non-linear, and the same distance would be crossed again in roughly seventeen hours, then five, then one, then under three minutes. These predictions were all subject to error, and the exact moment of the burst remained uncertain by at least an hour, but the most likely swath of possibilities all placed Lacerta well above the horizon at Atlanta. For a hemisphere stretching from the Amazon to the Yangtse, the ozone layer would be blasted away in an instant. In Atlanta, it would happen beneath the blazing afternoon sun.

The path Orlando had taken when escorting them out of the enclave was still stored in the gleisners' navigation systems. They pushed through the undergrowth as fast as they could, hoping to trigger alarms and attract attention.

Yatima heard branches move suddenly, off to their left. Ve called out hopefully, "Orlando?" They stopped and listened, but there was no reply.

Inoshiro said, "It was probably just an animal."

"Wait. I can see someone."

"Where?"

Yatima pointed out the small brown hand holding a branch, some twenty meters away trying to release it slowly, instead of letting it spring back into place. "I think ve’s a child."

Inoshiro spoke loudly but gently in Modern Roman. "We’re friends! We have news!"

Yatima adjusted the response curve of the gleisner’s visual system, optimizing it for the shadows behind the branch. A single dark eye stared back through a gap between the leaves. After a few seconds, the hidden face shifted cautiously, choosing another peephole; Yatima reconstructed the blur into a jagged strip of skin joining two lemur eyes.

Ve showed the partial image to the library, then passed the verdict to inoshiro. "Ve’s a dream ape."

"Shoot ver."

"What?"

"Shoot ver with the Introdus!" Inoshiro remained motionless and silent, speaking urgently in IR. "We can’t leave ver to die!"

Isolated by the frame of leaves, the dream ape’s eye appeared eerily expressionless. "But we can’t force ver—"

"What do you want to do? Give ver a lecture in neutron star physics? Even the bridgers can’t get through to dream apes! No one’s going to explain the choices to ver—not now, not ever!"

Yatima insisted stubbornly, "We don’t have the right to do it by force. Ve’d have no friends inside, no family—"

Inoshiro made a sound of disgust and disbelief. "We can clone ver some friends! Give ver a scape just like this, and ve’d barely know the difference."

"We’re not here to kidnap people. Imagine how you’d feel, if some alien creature reached into the polis and dragged you away from everything you knew—"

Inoshiro almost screamed with frustration. "No, you imagine how this flesher will feel, when vis skin’s burnt so badly that the fluid beneath starts seeping out!"

Yatima felt a wave of doubt sweep through ver. Ve could picture the whole, hidden dream ape child, standing there waiting fearfully for the strangers to pass and though ve could barely comprehend the idea of physical pain, images of bodily integrity resonated deeply. The biosphere was a disordered world, full of potential toxins and pathogens, ruled by nothing but the chance collisions of molecules. A ruptured skin would be like a wildly malfunctioning exoself that let data flood across its borders at random, overwriting and corrupting the citizen within.

Ve said hopefully, "Maybe vis family will find a cave to shelter in, once they notice the effects of the UV. That’s not impossible; the canopy will protect them for a while. They could live on fungi—"

"I’ll do it." Inoshiro grabbed Yatima’s right arm, and swung it toward the child. "Give me control of the delivery system, and I’ll do it myself."

Yatima tried to pull free. Inoshiro resisted. The struggle confused their separate copies of the interface, which was too stupid to realize it was fighting itself; they both overbalanced. As ve toppled into the undergrowth, Yatima almost felt it: the descent, the inevitable impact. Helplessness. Ve could hear the child running away.

Neither of them moved. After a while, Yatima said, "The bridgers will find a way to protect them. They’ll engineer some kind of shield for their skin. They could release the genes in a virus—"

"And they’ll do all this in a day? Before or after they work out how to feed fifteen thousand people when their crops are wilting, the ground is frozen, and the rain’s about to turn into nitric acid?"

Yatima had no reply. Inoshiro rose to vis feet, then pulled ver up. They walked on in silence.

Halfway to the edge of the jungle, they were met by three bridgers, two females and a male. All were fully grown, but young-looking, and wary. Communication proved difficult.

Inoshiro repeated patiently, "We are Yatima and Inoshiro. We came here once before, twenty-one years ago. We’re friends."

The man said, "All your robot friends are on the moon; none of them are here now. Leave us in peace." The bridgers remained several meters away; they’d retreated in alarm when Yatima had approached them with an outstretched hand.

Inoshiro complained in IR, "Even if they’re too young to remember… our last visit should he legendary."

"Apparently not."

Inoshiro persisted. "We’re not gleisners! We’re from Konishi polis; we’re just riding these machines. We’re friends of Orlando Venetti and Liana Zabini." The bridgers showed no sign of recognizing either name; Yatima wondered soberly if it was possible that they were both dead. "We have important news."

One of the women asked angrily, "What news? Tell us, then leave!"

Inoshiro shook vis head firmly. "We can only give our news to Orlando or Liana." Yatima agreed with this stand; a garbled account, half-understood, would do untold damage.

Inoshiro asked in IR, "What do you think they’d do if we just marched into the city?"

"They’d stop us."

"How?"

"They must have weapons of some kind. It’s too risky; we’ve both used up most of our maintenance nanoware—and anyway, they’re never going to trust us if we barge in uninvited."

Yatima tried addressing the bridgers verself. "We are friends, but we’re not getting through to you. Can you find a translator?" The second woman was almost apologetic. "We have no robot translators."

"I know. But you must have translators for statics. Think of us as statics."

The bridgers exchanged bemused glances, then went into a huddle, whispering.

The second woman said, "I’ll bring someone. Wait."

She left. The other two stood guard over them, refusing to be drawn into further conversation. Yatima and Inoshiro sat on the ground, facing each other rather than the fleshers, hoping to put them at ease.

By the time the translator arrived it was late afternoon. She approached and shook their hands, but regarded them with undisguised suspicion.

"I’m Francesca Canetti. You claim to be Yatima and Inoshiro, but anyone could he inhabiting these machines. Can you tell me what you saw here? What you did?"

Inoshiro recounted the details of their visit. Yatima suspected that their frosty reception was partly due to Carter-Zimmerman’s well-intentioned "assault" on the fleshers' communications network, and ve felt a renewed pang of shame. Ve and Inoshiro had had twenty-one years in which to re-establish a secure gateway between the networks; even with the problems of subjective time differences, that might have led to some kind of trust by now. But they’d done nothing.

Francesca said, "So what’s the news you’ve brought us?"

Inoshiro asked her, "Do you know what a neutron star is?"

"Of course." Francesca laughed, clearly offended. "That’s a rich question, coming from a couple of lotus-eaters." Inoshiro remained silent, and after a moment Francesca elaborated, in a tone of controlled resentment. "It’s a supernova remnant. The dense core left behind when a star is too massive to form a white dwarf, but not massive enough to forms a black hole. Should I go on, or is that enough to satisfy you that you’re not dealing with a hunch of agrarian throwbacks who’ve regressed to pre-Copernican cosmology?"

Inoshiro and Yatima conferred in IR, and decided to risk it. Francesca seemed to understand them as well as Orlando and Liana; stubbornly holding out for their old friends would cause too much hostility, and waste too much time.

Inoshiro explained the situation very clearly—and Yatima resisted interjecting with provisos and technicalities—but ve could see Francesca growing ever more suspicious. It was a long, long chain of inferences from the faint waves picked up by TERAGO to the vision of a frozen, UV-blasted Earth. With an asteroid or comet, the fleshers could have used their own optical telescopes to reach their own conclusions, but they lead no gravitational wave detectors. Everything had to be taken on trust, third hand.

Finally, Francesca admitted, "I don’t understand this well enough to question you properly. Will you come into the city and address a convocation?"

Inoshiro said, "Of course."

Yatima asked, "You mean we’ll talk to representatives of all the bridgers, through translators."

"No. A convocation means all the fleshers we can contact. Not just talking to Atlanta. Talking to the world."

* * *

As they made their way through the jungle, Francesca explained that she knew Liana and Orlando well, but Liana was sick, so no one had yet troubled them with the news that the Konishi emissaries had returned.

When Atlanta came into view ahead, surrounded by its vast green and golden fields, it was as if the scale of the problems the bridgers would soon be facing had been laid out for inspection in hectares of soil, megaliters of water, tons of grain. In principle, there was absolutely no reason why suitably adapted organic life couldn’t flourish in the new environment Lacerta would create. Crops could employ robust pigments that made use of UV photons, their roots secreting glycols to melt the hardest tundra, their biochemistry adapted to the acidic, nitrogenous water and soil. Other species essential to the medium-term chemical stability of the biosphere could be given protective modifications, and the fleshers themselves could engineer a new integument to shield them from cell death and genetic damage even in direct sunlight.

In practice, though, any such transition would be a race against time, constrained at every step by the realities of mass and distance, entropy and inertia. The physical world couldn’t simply be commanded to change; it could only be manipulated, painstakingly, step by step—more like a mathematical proof than a scape.

There were low, dark clouds rolling over the city as they approached. On the main avenue, people stopped to watch the robots arriving with their escort, but the crowds seemed strangely lethargic in the shadowless light. Yatima could see that their clothes were damp, their faces shiny with perspiration. The gleisner’s skin told ver the ambient temperature and humidity: 40 degrees Celsius, 93 percent. Ve checked with the library; this was not generally considered pleasant, and there could be metabolic and behavioral consequences, depending on each exuberant’s particular adaptations.

A few people greeted them, and one woman went s far as to ask why they’d returned. Yatima hesitated, and Francesca intervened. "The emissaries will address a convocation soon. Everyone will hear their news, then."

They were taken to a large, squat, cylindrical building near the center of the city, and led through the foyer and down a corridor to a room dominated by a long wooden table. Francesca left them with the three guards—it was impossible to think of them as anything else—saying she’d return in an hour or two. Yatima almost protested, but then ve recalled Orlando saying that it would take days to gather all the bridgers together. Arranging a planet-wide convocation in an hour—to discuss claims by two self-declared but possibly fraudulent Konishi citizens of an imminent threat to all life on Earth—would be a major feat of diplomacy.

They sat on one side of the long table. Their guards remained standing, and the silence seemed tense. These people had heard the whole conversation about Lacerta, but Yatima wasn’t sure what they’d made of it.

After a while, the man asked nervously, "You talked about radiation from space. Is this the start of a war?"

Inoshiro said firmly, "No. It’s a natural process. It’s probably happened to the Earth before, hundreds of millions of years ago. Maybe many times." Yatima refrained from adding: Only never this close, never this strong.

"But the stars are falling together faster than they should be. So how do you know they’re not being used as a weapon?"

"They’re falling together faster than astronomers thought they would. So the astronomers were wrong, they misunderstood some of the physics. That’s all."

The man seemed unconvinced. Yatima tried to imagine an alien species with the retarded morality required for warfare and the technological prowess to manipulate neutron stars. It was a deeply unpleasant notion, but about as likely as the influenza virus inventing the H-bomb. The three bridgers spoke together quietly, but the man remained visibly agitated. Yatima said reassuringly, "Whatever happens, you’re always welcome in Konishi. Whoever wants to come."

The man laughed, as if he doubted it.

Yatima raised vis right hand, displaying his index finger. "No, it’s true. We’ve brought enough Introdus nanoware—"

Inoshiro was sending warning tags even before the expression on the man’s face changed. He leant forward and grabbed Yatima’s hand by the wrist, then slammed it down on the table. He screamed, "Someone get a torch! Get a cutting tool!" One of the guards left the room; the other approached warily.

Inoshiro said calmly, "We would never have used it on anyone without permission. We just wanted to be prepared to offer you migration, if things went badly."

The man raised his free hand toward ver in a fist. "You keep back!" Sweat was dripping from his face; Yatima was doing nothing to resist, but the gleisner’s skin reported that the man was straining hard against it, as if he was wrestling with some monstrous opponent.

He spoke to Yatima, without taking his eyes off Inoshiro. "What’s really going to happen? Tell me! Will the gleisners set off their bombs in space, so you can herd the last of us into your machines?"

"The gleisners have no bombs. And they respect you much more highly than they respect us; the last thing they’d want to do is force fleshers into the polises." They’d faced some strange misconceptions before, but nothing like this level of paranoia.

The woman returned, carrying a small machine with a metal rod shaped into a semi-circle protruding from one end. She touched a control and an arc of blue plasma appeared, joining the tips of the rod. Yatima instructed the Introdus nanoware to begin crawling up the repair system ducts in vis arm, back toward his torso. The man leaned down harder than ever, then the woman approached and began slicing through the limb, high above the elbow.

Yatima didn’t waste the nanoware’s energy by pestering it with a stream of queries; ve just waited for the strange experience to be over. The interface didn’t know what to make of the damage reports from the gleisner’s hardware—and it declined to reach into Yatima’s self-symbol and perform matching surgery. When the plasma arc broke through to the other side and the man pulled the robot’s severed arm away, the corresponding part of Yatima’s icon was left mentally protruding from the stump-a kind of phantom presence, only half-free of the feedback loop of embodiment.

When ve dared to check, fifteen doses of the Introdus nanoware had made it to safety. The rest were lost, or heat-damaged beyond repair.

Yatima met the man’s eyes and said angrily, "We came here in peace; we would never have violated your autonomy. But now you’ve limited the choices for others." Without a word, the man placed the plasma saw on the edge of the table and began feeding the gleisner’s hand back and forth through the arc, reducing the delicate machinery to slag and smoke. When Francesca returned, she seemed equally outraged by the guards' revelation that nanoware had been brought into the enclave, and the less-than-diplomatic ad hoc remedy they’d employed to deal with it.

Under the Treaty of 2190, Yatima and Inoshiro should have been expelled from Atlanta immediately, but Francesca was prepared to bend the rules to allow them to address the convocation—and to Yatima’s surprise, the guards agreed. Apparently they believed that a public interrogation by the assembled fleshers would be the best way to expose the gleisner-Konishi conspiracy.

As they walked down the corridor toward the Convocation Hall, Inoshiro said in IR, "They can’t all be like this. Remember Orlando and Liana."

"I remember Orlando ranting about the evil gleisners and their wicked plans."

"And I remember Liana setting him straight."

The Convocation Hall was a large cylindrical space, roughly the same shape as the building itself. Concentric rows of seats converged on a circular stage—and there were about a thousand bridgers filling them. Behind and above the seats, on the cylinder’s wall, giant screens displayed the images of representatives from other enclaves. Yatima could easily distinguish the avian and amphibian exuberants, but ve had no doubt that the unmodified appearance of the others hid a greater range of variation.

The dream apes were not represented.

The guards stayed behind as Francesca led them up onto the stage. It was divided into three tiers; nine bridgers stood on the outermost tier, facing the audience, and three stood on the second.

"These are your translators," Francesca explained. "Pause after every sentence, and wait for all of them to finish." She pointed out a slight indentation on the stage, at the very center. "Stand here to be heard; anywhere else, you’ll be inaudible." Yatima had already noticed the unusual acoustics—they’d walked through excesses and absences of background noise, and the intensity of Francesca’s voice had fluctuated strangely. There were complex acoustic mirrors and baffles hanging from the ceiling, and the gleisner’s skin had reported sudden air pressure gradients which were probably due to some form of barrier or lens.

Francesca took center stage and addressed the convocation. "I am Francesca Canetti of Atlanta. I believe I am presenting to you Yatima and Inoshiro of Konishi polis. They claim to bring serious news, and if it’s true it concerns us all. I ask you to listen to them carefully, and question them closely."

She stepped aside. Inoshiro muttered in IR, "Nice of her to inspire such confidence in us."

Inoshiro repeated the account of Lacerta G-1 that ve’d given to Francesca in the jungle, pausing for the translators and clarifying some terms in response to their queries. The inner tier of three translators spoke first, then the outer nine offered their versions; even with the acoustics arranged to allow some of them to speak simultaneously, it was painfully slow. Yatima could understand that automating the process would have gone against the bridgers' whole culture, but they still should have had some more streamlined way to communicate in an emergency. Or maybe they did, but only for a predetermined set of natural disasters.

As Inoshiro began describing the predicted effects on the Earth, Yatima tried to judge the mood of the audience. Flesher gestalt, limited by anatomy, was much more subdued than the polis versions, but ve thought ve could detect a growing number of faces expressing consternation. There was no dramatic change sweeping through the hall, but ve decided to interpret this optimistically: anything was better than panic.

Francesca moderated the responses. The first came from the representative of an enclave of statics; he spoke a dialect of English, so the interface slipped the language into Yatima’s mind.

"You are shameless. We expect no honor from the simulacra of the shadows of departed cowards, but will you never give up trying to wipe the last trace of vitality from the face of the Earth?" The static laughed humorlessly. "Did you honestly believe that you could frighten us with this risible fairy-tale of quarks and gamma rays raining from the sky, and then we’d all file meekly into your insipid virtual paradise? Did you imagine that a few cheap, shocking words would send us fleeing from the real world of pain and ecstasy into your nightmare of perfectibility?" He gazed down at them with a kind of fascinated loathing. "Why can’t you stay inside your citadels of infinite blandness, and leave us in peace? We humans are fallen creatures; we’ll never come crawling on our bellies into your ersatz Garden of Eden. I tell you this: there will always be flesh, there will always be sin, there will always be dreams and madness, war and famine, torture and slavery."

Even with the language graft, Yatima could make little sense of this, and the translation into Modern Roman was equally opaque. Ve dredged the library for clarification; half the speech seemed to consist of references to a virulent family of Palestinian theistic replicitors.

Ve whispered to Francesca, dismayed, "I thought religion was long gone, even among the statics."

"God is dead, but the platitudes linger." Yatima couldn’t bring verself to ask whether torture and slavery also lingered, but Francesca seemed to read vis face, and added, "Including a lot of confused rhetoric about free will. Most statics aren’t violent, but they view the possibility of atrocities as essential for virtue—what philosophers call ‘the Clockwork Orange fallacy.’ So in their eyes, autonomy makes the polises a kind of amoral Hell, masquerading as Eden."

Inoshiro was struggling to respond, in English. "We don’t ask you to come into the polises if you don’t wish to. And we aren’t lying in order to frighten you; we only want you to be prepared."

The static smiled serenely. "We are always prepared. This is our world, not yours; we understand its perils."

Inoshiro began to speak earnestly about shelter, fresh water, and the options for a viable food supply. The static interrupted ver, laughing loudly. "The final insult was choosing the millennium. A superstition for addled children."

Inoshiro was bewildered. "But that’s gigatau away!"

"Close enough to make your contempt transparent." The static bowed mockingly, and his image vanished.

Yatima gazed at the blank screen, unwilling to accept what it seemed to imply. Ve asked Francesca, "Will others in his enclave have heard Inoshiro speak?"

"A few, almost certainly."

"And they could choose to go on listening?"

"Of course. No one censors the net."

There was still hope, then. The statics weren’t entirely beyond reach, like the dream apes.

The next response came from an unmodified-looking exuberant woman, speaking a language unfamiliar to the library. When the translation came, she turned out to be asking for more details of the process that was assumed to be robbing the neutron stars of their angular momentum.

Inoshiro had grafted extensive knowledge of Kozuch Theory into vis mind, and ve had no trouble answering; Yatima, wanting to stay fresh for the Mines, understood slightly less. But ve did know that the computations linking Kozuch’s Equation to the neutron stars' dynamics were intractably difficult, and it was mainly just a process of elimination that had left polarization as the most plausible theory.

The exuberant listened calmly; Yatima couldn’t tell if this was mere courtesy, or a sign that someone was taking them seriously at last. When the outer-tier translator was finished, the exuberant made a further comment.

"With such low tidal forces it would take many times longer than the lifetime of the universe for the runaway polarization state to tunnel through the energy barrier and dominate the confinement state. Polarization cannot he the cause." Yatima was astonished. Was this confident assertion misplaced—or a mistranslation—or did the exuberant have a solid mathematical reason for it? "However, I accept that the observations are unambiguous. The neutron stars will collide, the gamma-ray flash will occur. We will make preparations."

Yatima wished she could have said more, but with twelve translators involved a prolonged discussion on the subject would have taken days. And they’d finally had one small victory, so ve savored it; a post mortem of the neutron stars' physics could wait.

As Francesca chose the next speaker, several people in the audience stood and began making their way out. Yatima decided to treat this as a good sign: even if they weren’t entirely convinced, they could set in motion precautionary steps that would save hundreds or thousands of lives.

With extensive mind grafts, and the library at vis disposal, Inoshiro fielded technical questions easily. When the amphibious exuberant asked about UV damage to plankton and pH changes in the surface waters of the oceans, there was a Carter-Zimmerman model to quote. When a bridger in the audience questioned TERAGO’s reliability, Inoshiro explained why cross-talk from some other source couldn’t be the cause of the neutron stars' ever quickening waves. From the subtleties of photochemistry in the stratosphere to the impossibility of Lacerta’s soon-to-be-born black hole forming fast enough to swallow all the gamma rays and spare the Earth, Inoshiro countered almost every objection that might have made the case for action less compelling.

Yatima was filled with uneasy admiration. Inoshiro had pragmatically become exactly what the crisis required ver to become, grafting in all this second-hand understanding without regard for the effects on vis own personality. Ve would probably choose to have most of it removed afterward; to Yatima this sounded like dismemberment, but Inoshiro seemed to view the whole prospect as less traumatic than the business of taking on and shrugging off their gleisner bodies.

More enclave representatives began signing off; some clearly persuaded, some obviously not, some giving no signals that Yatima could decipher. And more bridgers left the hall, but others came in to take their place, and some Atlanta residents asked questions from their homes.

The three guards had sat in the audience and let the debate run its course, but now the woman who’d sliced off Yatima’s arm finally lost patience and sprang to her feet. "They brought Introdus nanoware into the city! We had to cut the weapon from vis body, or they would have used it by now!" She pointed at Yatima. "Do you deny it?"

The bridgers responded to this accusation the way Yatima had expected them to greet the news of the burst: with an audible outcry, agitated body movements, and some people rising to their feet and yelling abuse at the stage.

Yatima took Inoshiro’s place at the acoustic focus. "It’s true that I brought in the nanoware, but I would only have used it if asked. The nearest portal is a thousand kilometers away; we only wanted to offer you the choice of migration without the risks of that long journey."

There was no coherent response, just more shouting. Yatima looked around at the hundreds of angry fleshers, and struggled to understand their hostility; they couldn’t all be as paranoid as the guards. Lacerta itself was a crushing blow, a promise of decades of hardship, at best… but maybe talk of "the choice of migration" was worse. Lacerta could only drive them into the polises if it could hammer them into the ground; maybe the prospect of following the Introdus seemed less like a welcome escape hatch, a means of cheating death, than a humiliating means of allowing the fleshers to witness their own annihilation.

Yatima raised vis voice to ensure that the translators could hear ver. "We were wrong to bring in the nanoware—but we’re strangers, and we acted out of ignorance, not malice. We respect your courage and tenacity, we admire your skills—and all we ask is to be allowed to stand beside you and help you fight to go on living the way you’ve chosen to live: in the flesh."

This seemed to split the audience; some responded with jeers of derision, some with renewed calm and even enthusiasm. Yatima felt like ve was playing a game ve barely understood, for stakes ve hardly dared contemplate. They had never been fit for this task, either of them. In Konishi, the grossest acts of foolishness could barely wound a fellow citizen’s pride; here and now, a few poorly judged words could cost thousands of lives.

One bridger called out words that were translated as, "Do you swear that you have no more Introdus nanoware—and will make no more?"

This question silenced the hall. Trust the bridgers in their diversity to have someone who knew the workings of a gleisner body. The guards glared up at Yatima, as if ve’d misled them merely by failing to confess the existence of these possibilities.

"I have no more, and I will make no more." Ve spread his arms, as if to show them the innocent phantom protruding from the stump, incapable of touching their world.

* * *

The convocation stretched on through the night. People came and went, some splitting off into groups to coordinate preparations for the burst, some returning with new questions. In the early hours of the morning, the three guards called on the meeting to expel Yatima and Inoshiro from Atlanta immediately; upon losing the vote they walked out.

By dawn, most of the bridgers and the representatives of many of the enclaves seemed to have been won over, if only to the point where they accepted that the balance of probabilities made it well worth the risk of wasting effort on unnecessary precautions. At seven o’clock, Francesca told the second shift of translators to get some sleep; the hall wasn’t quite empty, but the few people remaining were absorbed in their own urgent discussions, and the wallscreens were blank.

One of the bridgers had suggested that they find a way to get the TERAGO data onto the fleshers' communications network. Francesca took them to Atlanta’s communications hub—a large room in the same building—and they worked with the engineer on duty to establish a link to the Coalition via the drones. Translating the gestalt tags into suitable audiovisual equivalents looked like it would be the hardest part, but there turned out to be a centuries-old tool in the library for doing just that.

When everything was working the engineer summoned a plot of the Lacerta gravity waves and an annotated image of the neutron stars' orbit onto two large screens above her console: stripped-down versions of the rich polis scapes playing as flat, framed pictures. Compared to the historical baseline, the waves had doubled in frequency and their power had risen more than tenfold. G-1a and G-1b were still a little more than 300,000 kilometers apart, but the higher-derivative trends continued to imply a sudden, sharp fall around 20:00 UT—two p.m. local tune—and any flesher on the planet with minimal computing resources could now take the raw data and confirm that. Of course, the data itself could have been fabricated, but Yatima suspected it would still be more convincing than vis word, or Inoshiro’s, alone.

"I’m going to need a few hours' rest." Francesca had developed a fixed gaze and monotone speech; her skepticism about the burst had clearly faded long ago, but she’d shown no sign of emotion, and she’d kept the convocation running to the end. Yatima wished ve could offer her some kind of comfort, but the only thing within vis gift was poisonous, unmentionable "I don’t know what your plans are now."

Neither did Yatima, but Inoshiro said, "Can you take us to Liana and Orlando’s house?"

Outside, people were constructing covered walkways between buildings, wheeling sacks and barrels of food into repositories, digging trenches and laying pipes, spreading tarpaulins to make new corridors of shade. Yatima hoped the message had got through that even reflected UV would soon have the power to burn or blind; some of the bridgers working in the heat had bare limbs or torsos, and every square centimeter of skin seemed to radiate vulnerability. The sky was darker than ever, but even the heaviest clouds would make a weak and inconstant shield. The crops in the fields were as good as dead; medium-term survival would come down to the ability to design, create, plant, and harvest viable new species before existing food supplies ran out. There was also the question of energy; Atlanta was largely powered by photovoltaic plants tailored to the atmosphere’s current spectral windows. Carter-Zimmerman’s botanists had already offered some tentative suggestions; Inoshiro had sketched the details at the convocation, and now they were available in full, on-line. No doubt the fleshers would regard them as the work of model-bound dilettante theoreticians, but as starting points for experimentation they had to be better than nothing.

They reached the house. Orlando looked tired and distracted, but he greeted them warmly. Francesca left, and the three of them sat in the front room.

Orlando said, "Liana’s sleeping. It’s a kidney infection, a viral thing." He stared at the space between them. "RNA never sleeps. She’s going to be all right, though. I told her you’d returned. She was pleased."

"Maybe Liana will design your new skin and corneas," Yatima suggested. Orlando made a polite sound of agreement.

Inoshiro said, "You should both come with us."

"Sorry?" Orlando rubbed his bloodshot eyes.

"Back into Konishi." Yatima turned to ver, appalled; ve’d told ver about the surviving nanoware, but after the reactions they’d had so far, this was madness.

Inoshiro continued calmly, "You don’t have to go through any of this. The fear, the uncertainty. What if things go badly, and Liana’s still sick? What if you can’t travel to the portal? You owe it to her to think about that now." Orlando didn’t look at ver, and didn’t reply. After a moment, Yatima noticed tears running into his beard, barely visible against the sheen of sweat. He cradled his head in his hands, then said, "We’ll manage."

Inoshiro stood. "I think you should ask Liana."

Orlando raised his head slowly; he looked more astonished than angry. "She’s asleep!"

"Don’t you think this is important enough to wake her? Don’t you think she has a right to choose?"

"She’s sick, and she’s asleep, and I’m not going to put her through that. All right? Can you understand that?" Orlando searched Inoshiro’s face; Inoshiro gazed back at him steadily. Yatima suddenly felt more disoriented than at any time since they’d woken in the jungle.

Orlando said, "And she doesn’t fucking know yet." His voice changed sharply on the last word. He bunched his fists and said angrily, "What do you want? Why are you doing this?"

He stared at Inoshiro’s bland gray features, then suddenly burst out laughing. He sat there grimacing and laughing angrily, wiping his eyes on the back of his hand, trying to compose himself. Inoshiro said nothing.

Orlando rose from the chair. "Okay. Come on up. We’ll ask Liana, we’ll give her the choice." He started up the stairs. "Are you coining?"

Inoshiro followed him. Yatima stayed where ve was. Ve could make out three voices, but no words.

There was no shouting, but there were several long silences. After fifteen minutes, Inoshiro came down the stairs and walked straight out onto the street. Yatima waited for Orlando to appear. Ve said, "I’m sorry." Orlando raised his hands, let them drop, dismissing it all. He looked steadier, more resolved than before.

"I should go and find Inoshiro."

"Yeah." Orlando stepped forward suddenly, and Yatima recoiled, expecting violence. When had ve learned to do that? But Orlando just touched vis shoulder and said, "Wish us luck."

Yatima nodded and backed away. "I do."

Yatima caught sight of Inoshiro near the edge of the city.

"Slow down!"

Inoshiro turned to took at ver, but kept walking. "We’ve done what we came for. I’m going home."

Ve could have returned to Konishi from anywhere; there was no need to leave the enclave. Yatima willed vis viewpoint forward faster, and the interface switched the body’s gait into a different mode. Ve caught up with Inoshiro on the road between the fields.

"What are you afraid of? Getting stranded?" When the burst hit, part of the upper atmosphere would turn to plasma, so satellite communication would be disrupted for a while. "We’ll have enough warning from TERAGO to send back snapshots." And then? The more hostile bridgers might go as far as killing the messengers, once post-Lacerta realities began to strike home, but if it came to that they could always just erase their local selves before things became too unpleasant.

Inoshiro scowled. "I’m not afraid. But we’ve delivered the warning. We’ve spoken to everyone who was capable of listening. Hanging around any longer is just voyeuristic."

Yatima gave this serious thought. "That’s not true. We’re too clumsy to help much as laborers, but after the burst we’d be the only people here guaranteed immune to UV. Okay, they can cover themselves, protect their eyes, nothing’s impossible if they do it carefully. But two robots built for unfiltered sunlight might still be useful."

Inoshiro didn’t reply. Soft-edged shadows were racing across the fields from black filaments of cloud streaming low overhead. Yatima glanced back at the city; the clouds were piling up into structures like dark fists. Heavy rain might be good; cool the place down, keep people indoors, blunt the first shafts of UV. So long as it didn’t hide so much that it left the bridgers complacent.

"I thought Liana would understand." Inoshiro laughed bitterly. "Maybe she did."

"Understand what?"

Inoshiro shook vis head. It was strange to see ver in this robot body again, which looked more like Yatima’s enduring mental image of ver than vis current icon back in Konishi.

"Stay and help, Inoshiro. Please. You’re the one who remembered the bridgers. You’re the one who shamed me into coming here."

Inoshiro regarded ver obliquely. "Do you know why I gave you the Introdus nanoware? We could have swapped jobs, you could have made the drones."

Yatima shrugged. "Why?"

"Because I would have used it all by now. I would have shot every bridger I could. I would have gathered them all up and carried them away, whether they wanted it or not."

Inoshiro walked on down the smooth dirt road. Yatima stood and watched ver for a while, then headed back into the city.

Yatima wandered Atlanta’s streets and parks, offering information wherever ve dared, approaching anyone who wasn’t working unless they looked openly hostile. Even without official translators ve often found ve could communicate with small groups of people, with everyone pitching in to cover the gaps.

An incomprehensible "What are the boundaries of purity?" became: "Can the sky be trusted this far?"—with the speaker glancing at the clouds—which became: "If it rains today, will it burn us?"

"No. The acidity won’t rise for months; the nitric oxides will take that long to diffuse down from the stratosphere."

The translated answers sometimes sounded like they’d traversed a Mobius strip and returned inverted, but Yatima clung to the hope that all sense wasn’t evaporating along the way, that "up" wasn’t really turning to "down."

By midday the city looked abandoned. Or besieged, with everyone in hiding. Then ve spotted some people working on a link between two buildings, and even in the forty-degree heat they were wearing long-sleeved clothing, and gloves, and welding masks. Yatima was encouraged by their caution, but ve could almost sense the dispiriting, claustrophobic weight of the protective gear. The bridgers clearly retained an evolved acceptance of the constraints of embodiment, but it seemed that half the pleasure of being flesh came from pushing the limits of biology, and the rest from minimizing all other encumbrances. Maybe the maddest of the masochistic statics would relish every obstacle and discomfort Lacerta could impose on them, waxing lyrical about "the real world of pain and ecstasy" while the ultraviolet flayed them, but for most fleshers it would do nothing but erode the kind of freedom that made the choice of flesh worthwhile.

There was a seat suspended by ropes from a frame in one of the parks; Yatima recalled seeing people sitting on it and swinging back and forth, an eternity ago. Ve managed to sit without falling, holding tight to one rope with vis remaining hand, but when ve willed the interface to set the pendulum in motion, nothing happened. The software didn’t know how.

By one o’clock, the Lacerta waves had strengthened to a hundred times their old power level. There was no point any more in waiting for data to arrive from two or three of TERAGO’s scattered detectors in order to eliminate interference from other sources; the feed now came straight from Bullialdus in real time, and Lac G-1’s racing pulse was loud enough to drown out everything else in the sky. The waves were visibly "chirping," each one clearly narrower than its predecessor; the latest two peaks were just 15 minutes apart, which meant the neutron stars had crossed the 200,000 kilometer mark. In an hour that separation would be halved, then in a few more minutes it would vanish. Yatima had been clinging to a faint hope of a shift in the dynamics, but the gleisners' ever-steeper extrapolation had kept on proving itself right.

The seat wobbled. A half-naked child was tugging on the side, trying to get vis attention. Yatima stared at ver, speechless, wanting to wrap vis invulnerable polymer body around the child’s exposed skin. Ve looked about the deserted playground for an adult; there was no one in sight.

Yatima stood. The child abruptly started crying and screaming. Ve sat, stood, tried to sweep the child up in vis single arm, failed. The child banged its fist on the vacated seat. Yatima obeyed.

The child clambered onto vis lap. Yatima glanced nervously at the TERAGO scape. The child stretched vis arms out and held the ropes, then leaned back slightly. Yatima imitated the motion, and the seat responded. The child leaned forward, Yatima followed.

They swung together, ever higher, the child screaming with delight, Yatima torn between terror and joy. A few sparse drops of rain descended, and then the clouds around the sun thinned, and parted.

The sudden clarity of the light was shocking. Looking across the sunlit playground—with a viewpoint gliding smoothly through this world, at last—Yatima felt an overpowering sense of hope. It was as if the Konishi mind seed still encoded the instinctive knowledge that, in time, the darkest stormclouds would always clear, the longest night would always yield to dawn, the harshest winter would always be tempered by spring. Every hardship the Earth forced upon its inhabitants was bounded, cyclic, survivable. Every creature born in the flesh carried the genes of an ancestor who had lived through the most savage punishment this world could inflict.

No longer. Sunlight breaking through the clouds was a lie, now. Every instinct that proclaimed that the future could be no worse than the worst of the past was obsolete. And Yatima had long understood that, outside the polises, the universe was capricious and unjust. But it had never mattered, before. It had never touched ver.

Ve didn’t trust verself to halt the swing safely, so ve froze and let the motion die away, ignoring the child’s complaints. Then ve carried ver shrieking to the nearest building, where someone seemed to know where ve belonged, and snatched ver away angrily.

The stormclouds had closed in again. Yatima returned to the playground and stood motionless, watching the sky, waiting to learn the new limits of darkness.

The neutron stars made their last full orbit in under five minutes, 100,000 kilometers apart and spiraling in steeply. Yatima knew ve was witnessing the final moments of a process that had taken five billion years, but on a cosmic scale was about as rare and significant as the death of a mayfly. Gamma-ray observatories picked up the signature of identical events in other galaxies, five times a day.

Still, Lac G-1’s great age meant that the two supernovae which had left the neutron stars behind predated the solar system. Supernovae sent shockwaves rippling through surrounding clouds of gas and dust, triggering star formation. So it was not inconceivable that G-1a or G-1b had created the sun, and the Earth, and the planets. Yatima wished ve’d thought of this when Inoshiro was talking to the statics; renaming the neutron stars "Brahma" and "Shiva" might have carried the right kind of mythic resonance to penetrate their mythic stupor. The vacuous metaphor might have saved a few lives. Other than that, whether Lacerta giver-of-life was about to show the hand that takes, or whether it was preparing to rain gamma rays on the accidental children of another dead star altogether, the scars inflicted would be equally painful, and equally meaningless.

The signal from Bullialdus climbed, peaked at ten thousand times the old level, then dived. In the orbit scape, the two arms of the inward spiral twisted into perfect radial alignment, and the narrow cones of uncertainty flaring out from each branch of the orbit shrank and merged into a single translucent tunnel. Each neutron star made a microscopic target for the other, so a succession of near misses granting five or ten minutes' reprieve would not have been unthinkable, but the verdict was that all sideways motion had vanished to the limits of measurement. The neutron stars would merge at the first approach.

In twenty-one seconds.

Yatima heard a voice wailing with anguish. Ve looked away from the scapes and swept vis robot gaze across the playground, for a moment convinced that the flesher child had escaped vis parents and returned, that search parties were out beneath the threatening sky. But the voice was distant and muffled, and there was no one in sight.

Ten seconds.

Five.

Let all the models be wrong: let an event horizon swallow the blast. Let the gleisners be lying, faking the data: let the most paranoid flesher be right.

An auroral glow filled the sky, an elaborate dazzling curtain of pink and blue electrical discharges. For a moment Yatima wondered if the clouds had been seared away, but as vis eyes desaturated and adjusted their response ve could see that the light was shining right through. The clouds made a faint grubby overlay, like smudges of dirt on a window pane, while ethereal patterns edged in luminous white and green swirled behind them, delicate wisps and vortices of ionized gas tracing the flows of billion-ampere currents.

The sky dimmed then began to flicker, strobing at about a kilohertz. Yatima instinctively reached for the polis library, but the connection had been severed; the ionized stratosphere was radio-opaque. Why the oscillation? Was there a shell of neutrons outside the black hole, ringing like a bell as it slipped into oblivion, Doppler-shifting the last of the gamma rays back and forth?

The flicker persisted, far too long for the burst itself to be the cause. If the remnants of Lac G-1 weren’t vibrating, what was? The gamma rays had deposited all their energy high above the ground, blasting nitrogen and oxygen molecules apart into a super-heated plasma, and the electrons and positive ions in this plasma had a billion terajoules to dispose of before they could recombine. Most of this energy would be going into chemical changes, and some was clearly reaching the ground as light, but powerful currents surging through the plasma would also be generating low frequency radio waves, which would bounce back and forth between the Earth and the now-ionized stratosphere. That was the source of the flicker. Yatima recalled the C-Z analysis stating that these waves could do real damage under certain conditions, though any effects would he highly localized, and insignificant compared to the problems of UV and global cooling.

As the auroral light behind the clouds faded, a blue white spike flashed across the sky. Yatima had barely registered this when a second discharge forked between the Earth and the clouds. The thunder was too loud to be heard; the gleisner’s acoustic sensors shut down in self-defense.

The sky darkened suddenly, as if the hidden sun had been eclipsed; the plasma must have cooled enough to start forming nitric oxides. Yatima checked the tags from vis skin; the temperature had just dropped from 41 to 39, and it was still falling. Lightning struck again, close by, and in the flash ve saw a layer of dark, wind-streaked cloud moving overhead.

Ripples appeared in the grass, at first just flattening the blades, but then Yatima saw dust rising up between them. The air came in powerful gusts, and when the pressure rose so did the temperature. Yatima raised vis hand into the hot wind, and tried to feel it flowing past vis fingers, tried to grasp what it would mean to be touched by this strange storm.

Lightning hit a building on the far side of the playground; it exploded, showering glowing embers. Yatima hesitated, then moved quickly toward the burst shell. Patches of grass were burning nearby. Ve could see no one moving inside, but between the lightning flashes it was like a starless night, and as the embers and the grass fires sputtered out there was a moment when everything seemed blanketed, smothered by darkness. Yatima stretched the gleisner’s vision into infrared; there were patches of body-temperature thermal radiation among the wreckage, but the shapes were ambiguous.

People were shouting frantically, somewhere, but it didn’t seem to be coming from the building. The wind masked and distorted the sound, scrambling all cues for distance and direction, and with the streets deserted it was like being in a scape with a soundtrack of disembodied voices.

As Yatima approached the building, buffeted by the wind, ve saw that it was empty; the body-temperature regions were just charred wood. Then vis hearing cut out again and the interface lost balance. Ve hit the ground face down, an image lingering on vis retinas: vis shadow stretched out across the grass, black and sharp against a sea of blue light. When ve scrambled to vis feet and turned around, there were three more buildings charred and smoking, walls split open, ceilings collapsed. Ve ran back across the playground.

There were people stumbling out of the ruins, ragged and bleeding. Others were searching frantically through the debris. Yatima spotted a man half-buried in rubble, eyes open but expressionless, a black splintered length of wood lying across his body from thigh to shoulder. Ve reached down and grabbed one end of the beam, and managed to lift it and swing it away.

As ve squatted beside the man, someone started punching and slapping the back of vis head and shoulders. Ve turned to see what was happening, and the flesher began yelling incoherently and striking vis face. Still squatting, ve backed off from the injured man awkwardly, as someone else tried to pull vis assailant away. Yatima stood and retreated. The flesher screamed after ver, "Vulture! Leave us in peace!"

Confused and disheartened, Yatima fled.

As the storm intensified, the bridgers' hasty modifications were falling apart; crumpled tarpaulins were blowing down the street, and the ceilings of some of the walkways had come loose and crashed to the ground. Yatima looked up at the dark sky and switched to UV. Ve could just make out the disk of the sun, penetrating the stratospheric NOx easily at these wavelengths, but still veiled by the heavy clouds.

Inoshiro had been right, there was nothing ve could do; the bridgers would bury their dead, treat the injured, repair their damaged city. Even in a world where the darkness at noon could blind them, they’d find their own ways to survive. Ve had nothing to offer them.

The link to Konishi was still down, but ve wasn’t prepared to wait any longer. Yatima stood motionless in the street, listening to the cries of pain and mourning, preparing verself for extinction. To forget this would be nothing but a sweet relief; vis Konishi self would be free to remember the bridgers in happier times.

Then the sky roared, and the lightning descended like rain.

The street became a sequence of dazzling staccato images bathed in blue and white, shadows jumping wildly with each new jagged arc of light. Buildings began exploding one after another, a relentless cascade of sudden orange flashes spraying sparks and fist-sized lumps of burning wood. People appeared, ducking and screaming, panicked out of their vulnerable shelters. Yatima watched, helpless but transfixed. The dying stratospheric plasma had found a way to reach down to Earth, its radio frequency pulses pumping vast quantities of ions through the lower atmosphere, inducing a massive voltage difference between the stormclouds and the ground. But now the voltage had crossed the breakdown threshold of the dust-filled air below, and the whole system was short-circuiting, rapidly and violently. Atlanta just happened to be in the way. Local damage, insignificant on a global scale.

Yatima moved slowly through the actinic blaze, half hoping for a lightning strike and the mercy of amnesia, but unable to abandon the bridgers now by choice. Driven from their homes, people were cowering beneath the onslaught, many of them burnt, torn, bloodied. A woman strode past with her arms stretched wide and her face to the sky, shouting defiantly: "So what? So what?"

A child, a half-grown girl, sat in the middle of the street, the side of her face and one exposed arm a raw pink, weeping lymphatic fluid. Yatima approached her. She was shivering.

"You can leave all this behind. Come into the polises. Is that what you want?" She stared back, uncomprehending. One of her ears was bleeding; the thunder might have deafened her. Yatima delved into the instructions for the gleisner’s maintenance nanoware, and had it rebuild the lost delivery system in vis left forefinger. Then ve commanded the surviving Introdus doses to move into place.

Ve raised vis arm and aimed the delivery system at the girl, shouting "Introdus? Is that what you want?" She cried out and covered her face. Did that mean no, or was she just bracing herself for the shock?

The child began sobbing. Yatima backed away, defeated. Ve could save fifteen lives, ve could drag fifteen people out of this senseless inferno, but who could ve be sure even understood what ve was offering?

Francesca. Orlando. Liana.

Orlando and Liana’s house wasn’t far. Yatima steeled verself and pushed on through the chaos, past the shattered buildings and the terrified fleshers. The lightning was finally dying away—and the fireproof buildings had only burnt when directly hit—but the city had been transformed into a scene from the age of barbarism, when bombs had rained from the sky.

The house was partly standing, but unrecognizable; Yatima only knew ve’d found the right place because of the gleisner’s navigation system. The top story was gutted, and there were holes in the ceiling and walls of the ground floor.

Someone was kneeling in the shadows, picking away debris at the edge of a vast heap where the ashes of most of the top story seemed to have landed. "Liana?" Yatima broke into a run. The figure turned toward ver.

It was Inoshiro.

Inoshiro had half-exposed a corpse, all black dessicated flesh and white bone. Yatima looked down at it, then recoiled, disoriented. This charred skull was not a symbol in some jaded work of polis art; it was proof of the involuntary erasure of a living mind. The physical world could do that. The death of a cosmic mayfly could do that.

Inoshiro said, "It’s Liana."

Yatima tried to absorb this, but ve felt nothing, the idea meant nothing.

"Have you found-?"

"Not yet." Inoshiro’s voice was expressionless.

Yatima left ver, and began scanning the rubble in IR, wondering how long a corpse would remain warmer than its surroundings. Then ve heard a faint sound from the front of the house.

Orlando was buried beneath pieces of the ruptured ceiling. Yatima called Inoshiro, and they quickly uncovered him. He was badly injured; both his legs and one arm had been crushed, and a gash in his thigh was spurting blood. Yatima checked the link to Konishi—ve couldn’t even guess how to treat such wounds—but either the stratosphere was still ionized, or one of the drones had been lost in the storm.

Orlando stared up at them, ashen but conscious, eyes pleading for something. Inoshiro said flatly, "She’s dead." Orlando’s face contorted silently.

Yatima looked away and spoke to Inoshiro in IR. "What do we do? Carry him to a place where they can treat him? Fetch someone? I don’t know how this works."

"There are thousands of injured people. No one’s going to treat him; he’s not going to live that long."

Yatima was outraged. "They can’t leave him to die!"

Inoshiro shrugged. "You want to try finding a communications link and calling for a doctor?" Ve peered out through the broken wall. "Or do you want to try carrying him to the hospital, and see if he survives the trip?"

Yatima knelt beside Orlando. "What do we do? There are a lot of people hurt, I don’t know how long it will take to get help."

Orlando bellowed with pain. A weak shaft of sunlight had appeared, coming through a hole in the ceiling and illuminating the skin of his broken right arm. Yatima glanced up; the storm was over, the clouds were beginning to thin and drift away.

Ve moved to block the light, while Inoshiro crouched behind Orlando, half-lifted him under the arms, and dragged him over the rubble into the shade. The wound in his thigh left a thick trail of blood.

Yatima knelt beside him again. "I still have the Introdus nanoware. I can use it, if that’s what you want."

Orlando said clearly, "I want to talk to Liana. Take me to Liana."

"Liana’s dead."

"I don’t believe you. Take me to her." He was struggling for breath, but he forced the words out defiantly.

Yatima stepped back beneath the hole in the ceiling. In ordinary light the sun appeared as a meek orange disk through the stratosphere’s brown haze, but in UV it shone fiercely amidst a blaze of scattered radiation.

Ve left the room, and returned carrying Liana’s body one-handed by the collarbone. Orlando covered his face with his unbroken arm and wept loudly.

Inoshiro took the corpse away. Yatima knelt by Orlando a third time, and put vis hand on his shoulder clumsily. "I’m sorry she’s dead. I’m sorry that hurt you." Ve could feel Orlando’s body shaking with each sob. "What do you want? Do you want to die?"

Inoshiro spoke in IR. "You should have left when you had the chance."

"Yeah? So why did you come hack?"

Inoshiro didn’t reply. Yatima swung around to face ver. "You knew about the storm, didn’t you? You knew how bad it would be!"

"Yes." Inoshiro made a gesture of helplessness. "But if I’d said anything when we arrived, we might not have had a chance to speak to the other fleshers. And after the convocation, it was too late. It would have just caused panic."

The front wall creaked and lurched forward, breaking loose from the ceiling in a shower of black dust. Yatima sprang to vis feet and backed away, then fired the Introdus into Orlando.

Ve froze. The wall had struck an obstacle; it was tilted precariously, but holding. Waves of nanoware were sweeping through Orlando’s body, shutting down nerves and sealing off blood vessels to minimize the shock of invasion, leaving a moist pink residue on the rubble as flesh was read and then cannibalized for energy. Within seconds, all the waves converged to form a gray mask over his face, which bored down to the skull and then ate through it. The shrinking core of nanoware spat fluid and steam, reading and encoding crucial synaptic properties, compressing the brain into an ever-tighter description of itself, discarding redundancies as waste.

Inoshiro stooped down and picked up the end product: a crystalline sphere, a molecular memory containing a snapshot of everything Orlando had been.

"What now? How many do you have left?"

Yatima stared at the snapshot, dazed. Ve had violated Orlando’s autonomy. Like a lightning bolt, like a blast of ultraviolet, ve had ruptured someone else’s skin.

"How many?"

Yatima replied, "Fourteen."

"Then we’d better go use them while we can."

Inoshiro led ver out of the ruins. Yatima shot everyone they came across who looked close to death, and had no one to care for them—reading the snapshots immediately, piping the data in IR into vis gleisner’s memory. They’d taken twelve more bridgers when a mob led by the border guards found them.

They started cutting up Yatima first. Ve passed the snapshot data to Inoshiro, then followed.

Before they’d finished destroying vis old body, the link to Konishi returned. The drones had survived the storm.

6. Divergence

Konishi polis, Earth

24 667 272 518 451 CST

10 December 3015, 3:21:55.605 UT

Yatima looked down on the Earth through the window of the observation bay. The surface wasn’t entirely obscured by NOx, but most of it appeared in barely distinguishable shades of muted, rust-tinged gray. Only the clouds and the ice caps stood out, back-lighting the stratosphere impartially to reveal it as a vivid reddish-brown. Spread over the clouds, spread over the snow, it looked like decaying blood mixed with acid and excrement: tainted, corrosive, rotten. The wound left by Lacerta’s one swift, violent incision had festered for almost twenty years.

Ve and Inoshiro had constructed this scape together, an orbital way station where refugees could wake to a view of the world they’d left behind as surely as if they’d physically ascended beyond its acid snow and its blinding sky; in reality, they were a hundred meters underground in the middle of a wasteland, but there was no point confronting them with that claustrophobic and irrelevant fact. Now the station was deserted; the last refugees had moved on, and there’d be no more. Famine had taken the last surviving enclaves, but even if they’d hung on for a few more years, plankton and land vegetation were dying so rapidly that the planet would soon be fatally starved of oxygen. The age of flesh was over.

There’d been talk of returning, designing a robust new biosphere from the safety of the polises and then synthesizing it, molecule by molecule, species by species. Maybe that would happen, though support for the idea was already waning. It was one thing to endure hardship in order to go on living in a familiar form, another to he reincarnated in an alien body in an alien world, for the sake of nothing but the philosophy of embodiment. The easiest way by far for the refugees to re-create the lives they’d once led was to remain in the polises and simulate their lost world, and Yatima suspected that in the end most would discover that they valued familiarity far more than any abstract distinction between real and virtual flesh.

Inoshiro arrived, looking calmer than ever. The final trips they’d made together had been grueling; Yatima could still see the emaciated fleshers they’d found in one underground shelter, covered in sores and parasites, delirious with hunger. They’d kissed their robot benefactors' hands and feet, then vomited up the nutrient drink which should have healed their ulcerated stomach linings and passed straight into their bloodstreams. Inoshiro had taken that kind of thing badly, but in the last weeks of the evacuation ve’d become almost placid, perhaps because ve’d realized that the horror was coming to an end.

Yatima said, "Gabriel tells me there are plans in Carter-Zimmerman to follow the gleisners." The gleisners had launched their first inhabited fleet of interstellar craft fifteen years before, sixty-three ships heading out to twenty-one different star systems.

Inoshiro looked bewildered. "Follow them? Why? What’s the point of making the same journey twice?"

Yatima wasn’t sure if this was a joke, or a genuine misunderstanding. "They’re not going to visit the same stars. They’ll launch a second wave of exploration, with different targets. And they’re not going to mess about with fusion drives like the gleisners. They’re going in style. They plan to build wormholes."

Inoshiro’s face formed the gestalt for "impressed" with such uncharacteristic purity and emphasis that any inflection hinting at sarcasm would have been redundant.

"The technology might take several centuries to develop," Yatima admitted. "But it will give them the edge in speed, in the long run. Quite apart from being a thousand times more elegant."

Inoshiro shrugged, as if it was all of no consequence, and turned to contemplate the view.

Yatima was confused; ve’d expected Inoshiro to embrace the plan so enthusiastically that vis own cautious approval would seem positively apathetic. But if ve had to argue the case, so be it. "Something like Lac G-1 might not happen so close to Earth again for billions of years, but until we know why it happened, we’re only guessing. We can’t even be sure that other neutron star binaries will behave in the same way; we can’t assume that every other pair will fall together once they cross the same threshold. Lac G-1 might have been some kind of freakish accident that will never be repeated—or it might have been the best possible case, and every other binary might fall much sooner. We just don’t know." The old meson jet hypothesis had proved short-lived; no sign of the jets blasting their way through the interstellar medium had ever shown up, and detailed simulations had finally established that color-polarized cores, although strictly possible, were extremely unlikely.

Inoshiro regarded the dying Earth calmly. "What harm could another Lacerta do, now? And what could anyone do to prevent it?"

"Then forget Lacerta, forget gamma-ray bursts! Twenty years ago, we thought the greatest risk to the Earth was an asteroid strike! We can’t be complacent just because we survived this, and the fleshers didn’t; Lacerta proves that we don’t know how the universe works—and it’s the things we don’t know that will kill us. Or do you think we’re safe in the polises forever?"

Inoshiro laughed softly. "No! In a few billion years, the sun will swell up and swallow the Earth. And no doubt we’ll flee to another star first… but there’ll always be a new threat hanging over us, known or unknown. The Big Crunch in the end, if nothing else." Ve turned to Yatima, smiling. "So what priceless knowledge can Carter-Zimmerman bring back from the stars? The secret to surviving a hundred billion years, instead of ten billion?"

Yatima sent a tag to the scape; the window spun away from the Earth, then the motion-blurred star trails froze abruptly into a view of the constellation Lacerta. The black hole was undetectable at any wavelength, as quiescent in the region’s high vacuum as the neutron stars had been, but Yatima imagined a speck of distorted darkness midway between Hough 187 and 10 Lacertae. "How can you not want to understand this? It’s just reached across a hundred light years and left half a million people dead."

"The gleisners already have a probe en route to the Lac G-1 remnant."

"Which might tell us nothing. Black holes swallow their own history; we can’t count on finding anything there. We have to look further afield. Maybe there’s another, older species out there, who’ll know what triggered the collision. Or maybe we’ve just discovered the reason why there are no aliens crisscrossing the galaxy: gamma-ray bursts cut them all down before they have a hope of protecting themselves. If Lacerta had happened a thousand years ago, no one on Earth would have survived. But if we really are the only civilization capable of space travel, then we should be out there warning the others, protecting the others, not cowering beneath the surface—"

Yatima trailed off. Inoshiro was listening politely, but with a slight smile that left no doubt that ve was highly amused. Ve said, "We can’t save anyone, Yatima. We can’t help anyone."

"No? What have you been doing for the last twenty years, then? Wasting your time?"

Inoshiro shook vis head, as if the question was absurd.

Yatima was bewildered. "You’re the one who kept dragging me out of the Mines, out into the world! And now Carter-Zimmerman are going out into the world to try to keep what happened to the fleshers from happening to us. If you don’t care about hypothetical alien civilizations, you must still care about the Coalition!"

Inoshiro said, "I feel great compassion for all conscious beings. But there’s nothing to be done. There will always be suffering. There will always be death."

"Oh, will you listen to yourself? Always! Always! You sound like that phosphoric acid replicator you fried outside Atlanta!" Yatima turned away, trying to calm down. Ve knew that Inoshiro had felt the death of the fleshers more deeply than ve had. Maybe ve should have waited before raising the subject; maybe it seemed disrespectful to the dead to talk so soon about leaving the Earth behind.

It was too late now, though. Ve had to finish saying what ve’d come here to say.

"I’m migrating to Carter-Zimmerman. What they’re doing makes sense, and I want to be part of it."

Inoshiro nodded blithely. "Then I wish you well."

"That’s it? Good luck and bon voyage?" Yatima tried to read vis face, but Inoshiro just gazed back with a psychoblast’s innocence. "What’s happened to you? What have you done to yourself?"

Inoshiro smiled beatifically and held out vis hands. A white lotus flower blossomed from the center of each palm, both emitting identical reference tags. Yatima hesitated, then followed their scent.

It was an old outlook, buried in the Ashton-Laval library, copied nine centuries before from one of the ancient memetic replicators that had infested the fleshers. It imposed a hermetically sealed package of beliefs about the nature of the self, and the futility of striving… including explicit renunciations of every mode of reasoning able to illuminate the core beliefs' failings.

Analysis with a standard tool confirmed that the outlook was universally self-affirming. Once you ran it. you could not change your mind. Once you ran it, you could not be talked out of it. Yatima said numbly, "You were smarter than that. Stronger than that." But when Inoshiro was wounded by Lacerta, what hadn’t ve done that might have made a difference? That might have spared ver the need for the kind of anesthetic that dissolved everything ve’d once been?

Inoshiro laughed. "So what am I now? Wise enough to be weak? Or strong enough to be foolish?"

"What you are now—" Ve couldn’t say it.

What you are now is not Inoshiro.

Yatima stood motionless beside ver, sick with grief, angry and helpless. Ve was not in the fleshers' world anymore; there was no nanoware bullet ve could fire into this imaginary body. Inoshiro had made vis choice, destroying vis old self and creating a new one to follow the ancient meme’s dictates, and no one else had the right to question this, let alone the power to reverse it.

Yatima reached out to the scape and crumpled the satellite into a twisted ball of metal floating between them, leaving nothing but the Earth and the stars. Then ve reached out again and grabbed the sky, inverting it and compressing it into a luminous sphere sitting in vis hand.

"You can still leave Konishi." Yatima made the sphere emit the address of the portal to Carter-Zimmerman, and held it out to Inoshiro. "Whatever you’ve done, you still have that choice."

Inoshiro said gently, "It’s not for me, Orphan. I wish you well, but I’ve seen enough."

Ve vanished.

Yatima floated in the darkness for a long time, mourning Lacerta’s last victim.

Then ve sent the handful of stars speeding away across the emptiness of space, and followed them.

The conceptory observed the orphan moving through the portal, leaving Konishi polis behind. With access to public data, it knew of the orphan’s recent experiences; it also knew that another Konishi citizen had shared them, and had not made the same choice. The conceptory wasn’t interested in scattering Konishi shapers far and wide, like replicating genes; its goal was the efficient use of polis resources for the enrichment of the polis itself.

There was no way to prove causality, no way to he certain that any of the orphan’s mutant shapers really were to blame. But the conceptory was programmed to err on the side of caution. It marked the old, unmutated values for the orphan’s altered fields as the only valid codes, discarding all alternatives as dangerous and wasteful, never to be tried again.

Part Three

Paolo said decisively, "What comes next is the Forge. You helped design it, didn’t you?"

"I wouldn’t go that far. I played a minor role."

Paolo grinned. "Success has a thousand parents, but failure is an orphan."

Yatima rolled vis eyes. "The Forge was not a failure. But the Transmuters won’t want to hear about my towering contribution to analytic methods in relativistic electron plasma modeling."

"No? Well, I was never an insider at all, so whatever we tell them will have to come from you."

Yatima thought it over. "I knew the two people who really mattered." Ve smiled. "You could say it’s a love story."

"Blanca and Gabriel?"

"Maybe I should have said triangle."

Paolo was baffled. "Who else was involved?"

"I never met her myself. But I think you can guess who I mean."

7. Kozuch’s legacy

Carter-Zimmerman polis, Earth

24 667 274 153 236 CST

10 December 3015, 3:49:10.390 UT

Gabriel asked the Carter-Zimmerman library to show him every scheme on record for building a traversable wormhole. The problem had been studied long before the necessary technology was remotely within reach, both as an exercise in theoretical physics and as an attempt to map out the possibilities for future civilizations. It had seemed like an act of ingratitude, as well as a waste of resources, to discard the fruits of all this ancient labor and start again from scratch, so Gabriel had volunteered to sort through all the methods and machines advocated in the past and select the ten most promising candidates for detailed feasibility studies.

The library promptly constructed an indexscape with 3,017 different blueprints, laid out in a conceptual evolutionary tree which stretched across the scape’s imaginary vacuum for hundreds of kilodelta. Gabriel was taken aback for a moment; he’d been aware of the numbers, but the visible history of the subject was still an intimidating sight. People had been contemplating wormhole travel for almost a millennium; longer, counting the early designs based on classical General Relativity, but it was with the advent of Kozuch Theory that the field had truly flourished.

In Kozuch Theory, wormholes were everything. Even the vacuum was a froth of short-lived wormholes when examined at the Planck-Wheeler length of ten-to-the-minus-thirty-five meters. As early as 1955, John Wheeler had suggested that the apparently smooth space-time of General Relativity would turn out to be a tangled maze of quantum wormholes at this scale, but it was another idea of Wheeler’s—finally made to work, with spectacular success, by Renata Kozuch a hundred years later—that had transformed these wormholes from arcane curiosities far beyond the limits of detection into the most important structures in physics. The elementary particles themselves were the mouths of wormholes. Electrons, quarks, neutrinos, photons, W-Z bosons, gravitons, and gluons were all just the mouths of longer-lived versions of the fleeting wormholes of the vacuum.

Kozuch had labored for more than twenty years to refine this hypothesis, drawing together tantalizing but partial results from dozens of other specialties, cannibalizing everything from Penrose spin networks to the compactified extra dimensions of string theory. By including six sub-microscopic dimensions along with the usual four of space-time, she had shown how wormholes with different topologies could account for the properties of all the known particles. No one had directly observed a Kozuch-Wheeler wormhole, but after surviving a millennium of experimental tests the model was widely accepted, not as the best tool for most practical calculations, but as the definitive expression of the underlying order of the physical world.

Gabriel had learned Kozuch Theory in the womb, and it had always seemed to him to be the deepest, clearest picture of reality available. The mass of a particle was a consequence of the disruption it caused to a certain class of vacuum wormholes: those with virtual gravitons at both ends. Disturbing the usual pattern of connections between these wormholes made space-time effectively curved, much as a change in the weave of a basket could force the surface to bend by bringing parallel threads together. It also created a few loose threads: other wormholes squeezed out of the vacuum by the "tighter weave" wherever space-time was curved, giving rise to both Hawking radiation from black holes and the even fainter Unruh radiation of ordinary objects.

Charge, color, and flavor arose from similar effects, but with virtual photons, gluons, and W-Z bosons as the mouths of the vacuum wormholes involved, and the six rolled-up dimensions, to which gravitons were impervious, now playing a crucial role. Spin measured the presence of a certain kind of extra-dimensional twist in the wormhole mouth; each half-twist contributed half a unit of spin. Fermions, particles such as electrons with an odd number of half-twists, had wormholes which could themselves become twisted like ribbons; if an electron was rotated 360 degrees, its wormhole would gain or lose a definite twist, with measurable consequences. Bosons, such as photons, had full twists in their wormhole mouths, but a 360-degree rotation left them unchanged because the kinks in their wormholes canceled themselves out. A single boson could be "self-linked," the only opening into a wormhole which looped back on itself, or any number of identical bosons could share a wormhole. Fermions were always joined in even numbers; the simplest case was a particle at one end of the wormhole, with its antiparticle at the other.

Under the extreme space-rime curvature of the early universe, countless vacuum wormholes had been "squeezed from the weave" to take on a more tangible existence. Most had formed particle-antiparticle pairs like electrons and positrons, but more rarely they’d created less symmetric combinations, such as an electron at one end of the wormhole with a three-pronged branching into a triplet of quarks, making up a proton, at the other.

This was the origin of all matter. By sheer chance, the vacuum had shed slightly more electron-proton wormholes than their antimatter equivalent, positrons linked to antiprotons, before expanding and cooling to the point where particle production ceased. Without that tiny random excess, every last electron and proton would have been annihilated by a matching antiparticle, and there would have been nothing in the universe but the microwave background, reverberating through empty space.

Kozuch herself had pointed out in 2059 that if this version of Big Bang cosmology was correct, it meant that every surviving electron was linked to a proton, somewhere. Brand new wormholes with known endpoints could be manufactured at will, simply by creating pairs of electrons and positrons, but existing wormholes already crisscrossed interstellar space. After twenty billion years drifting through an evolving and expanding universe, many particles torn from the vacuum side-by-side would have ended up thousands of light years apart. Chances were, every grain of sand, every drop of water on Earth, contained gateways to each of the hundreds of billions of stars in the galaxy, and some that reached far beyond.

The catch was: nothing in the universe could pass through the wormhole mouth of an elementary particle. All the known particles possessed a single quantum unit of surface area, and the probability of any of them passing through another’s wormhole was precisely zero.

This problem was not insurmountable. When an electron and a positron collided, their wormholes were spliced together end-to-end, making the two colliding mouths vanish. In that case two gamma-ray photons were produced, but if the wormholes could be spliced, not electron-end to positron-end but electron-end to electron-end, the energy normally lost as gamma rays would be trapped, and would go into making the new, spliced wormhole wider.

Achieving this union would require concentrating a modest amount of energy—two gigajoules, enough to melt a six-ton block of ice—into a volume as much smaller than that ice block as an atom was smaller than the observable universe. Wormholes produced by electron-electron splicing would be traversable only by fundamental particles, but splicing together a few billion of them would further widen the resulting wormhole, rather than lengthening it, enabling a moderately sophisticated nanomachine to pass through.

Gabriel had heard it rumored that the gleisners had considered the wormhole option, but elected to put it aside for the next few millennia. Building conventional interstellar spacecraft must have seemed trivial compared to the kind of technology it would take to tear open the portals to the stars scattered at their feet. Still, with 3,017 designs to choose from there had to be one within Carter-Zimmerman’s reach, even if it took a thousand years to bring to fruition. Gabriel was undaunted by the time scale; he had long hoped for a grand scheme like this to make sense of his longevity. Without a purpose that spanned the centuries, he could only drift between interests and aesthetics, friends and lovers, triumphs and disappointments. He could only live a new life every gigatau or two, until there was no difference between his continued existence and his replacement by someone new.

Full of hope, he moved across the scape toward the first blueprint.

8. Short cuts

Carter-Zimmerman polis, Earth

51 479 998 754 659 CST

7 August 3865, 14:52:31.813 UT

Blanca floated through the latest world ve’d grown from a novel symmetry group and a handful of recursion formulae. Giant inverted pyramids floated above ver, sprouting luminous outgrowths like rococo chandeliers. Feathery planar crystals swirled and grew around ver, then began to collide and merge into strange new objects, random acts of origami performed with diamond and emerald films. Below ver, a vast terrain of mountains and canyons was eroding in fast motion, carved by a blizzard of diffusion laws into glistening green and blue mesas, impossible overhangs, towering stratified sculptures veined with minerals unknown to chemistry.

In Konishi, ve would probably have called this "mathematics." In C-Z, it was necessary to call it "art," since anything else suggested a virtual universe in direct competition with the real one. Blanca had been dismayed to see the other polises sink back into complacency after the initial shock of carnevale, but ve still chafed against C-Z’s growing orthodoxy when it proclaimed that to explore any system of rules that failed to illuminate the physics of reality amounted to pernicious solipsism. The beauty of the physical world had nothing to do with its power to harm that was just the dogma of the dead statics in another guise and everything to do with the simplicity and consistency of its laws. Blanca was unimpressed by claims that C-Z’s physicists and engineers toiled only in the service of protecting the Coalition from the next dangerous cosmic surprise. It was the elegance of Kozuch Theory and the grandeur of the Forge itself that had kept them going; if either the guiding principles or the design had been the slightest bit uglier, they would have packed it in long ago.

Gabriel appeared beside ver, his fur dusted immediately with tiny crystals. Blanca reached over and brushed his shoulders affectionately; he responded by pressing a hand into the darkness of vis chest, inducing a gentle warmth throughout the whole invaded space. The places where Blanca’s icon seemed to lose its tangible boundary were the most sensitive by far; they could be touched in three dimensions.

"We’ve had a neutralization in one ring." Gabriel seemed pleased, but nothing in his voice or gestalt betrayed the fact that the whole Forge group had been working toward this moment for the last eight centuries. Blanca nodded slightly, a gesture packed with warmth that only vis lover could have decoded.

Gabriel said, "Will you rush with me? Until confirmation?" He sounded slightly guilty to be asking.

The news would have just reached Earth that a positron in one of the Forge’s magnetic storage rings had lost its charge and escaped into the surrounding laser trap, 65 hours ago. But it would take almost three more hours—ten megatau—for the crucial matching result from the second ring at the opposite end of the accelerator to arrive. Gabriel had lived through every similar delay tau-by-tau until now, patiently accepting the glacial slowness of manipulating matter on the hundred-terameter scale, but Blanca had certainly never seen it as some great moral principle.

"Why not?" They held hands in a cobalt blue snowdrift while their exoselves synched and slowed; the scape was synched directly to Blanca’s mind, so it appeared to carry on at the same rate.

Ve watched Gabriel’s face as they waited, cheating the time by a mere factor of a million instead of jumping the gap in a single bound. Even if it wasn’t a moral issue, relating to the physical world could be a delicate balancing act. Should you dart from significant event to significant event, creating a life devoid of everything else? Probably not—but exactly how much subjective time should you endure between the moments you were, in all honesty, desperately waiting for? Gabriel had passed the time at the standard Coalition rate, mostly by immersing himself in elaborate schemes for the eventual deployment of the wormholes, in between his sparse contacts with the machinery of the Forge as it was constructed and tested. But he’d almost run out of future to plan; the last Blanca had heard, he’d mapped out a detailed strategy for the—careful, non-exponential—exploration of the entire universe. Local wormholes probably didn’t lead everywhere, since the mouths could only have traveled a certain distance since the time they were formed, but the closed, finite universe ought further than a few hundred million light years, there’d he wormholes in the galaxies at that distance which would reach as far again.

Gabriel’s mildly preoccupied expression changed to one of satisfaction, though nothing as dramatic as relief. "The other ring’s confirmed. We’ve grabbed both ends."

Blanca swung his arm, dislodging a flurry of blue crystals from his fur. "Congratulations." If the second neutralized positron had slipped out into space, it would have been impossible to find. With luck, they’d soon confirm that photons could pass through the wormhole, but a bombardment of either tiny mouth would only produce a trickle from the other.

Gabriel mused, "I keep wondering if we could have failed. I mean… we made a few mistakes in the design that we only discovered centuries later. And we hit those chaotic modes in the electron beams where the simulations broke down, so we had to map the whole state space empirically and find a way through by trial-and-error. We did a hundred thousand small things wrong, wasting time, making it harder. But could we ever have failed completely, beyond recovery? Beyond repair?"

"Isn’t that question slightly premature?" Blanca inclined vis head skeptically. "Assuming this isn’t a false alarm, you’ve just linked the two ends of the Forge. That’s a start, but you’re not quite staring down the runnel to Procyon yet."

Gabriel smiled airily. "We’ve proved the basic principle; the rest is just a matter of persistence. Until the neutralization of those positrons, Kozuch-Wheeler wormholes might have turned out to be nothing but a useful fiction: just another metaphor that gave the right predictions at low energies, but fell apart under closer scrutiny." He paused for a moment, looking slightly scandalized by his own words; it was a risk that the Forge group had rarely mentioned. "But now we’ve shown that they’re real, and that we understand how to manipulate them. So what can go wrong from here?"

"I don’t know. When it comes to interstellar wormholes, it might take longer than you think to find one that doesn’t lead straight into the heart of a star, or the core of a planet."

"That’s true. But a certain amount of matter in every system has to he in the form of small asteroids, or interplanetary dust—somewhere we can burrow out from easily. And even if our estimates are wrong by a factor of a thousand, it would still only take a year or two to find and enlarge each new usable wormhole. Would you call that failure? When the gleisners are exploring a new system every century and calling it success?"

"No." Blanca tried harder. "Okay, what about this? You’ve just proved that you can splice two identical, electron-positron wormholes together, at the electron ends. What if it doesn’t work when you substitute a proton for one of the positrons?" Only primordial electron-proton wormholes offered the chance of an instant short-cut to the stars; the current experiment was using freshly created electron-positron pairs merely for the sake of having both ends of each wormhole accessible. Working exclusively with electron-proton wormholes might have been simpler in theory, but new ones with known endpoints couldn’t be created at useful rate under anything less than Big Bang conditions. Gabriel hesitated, and for a moment Blanca wondered if he’d taken the scenario to heart.

"That would be a setback," he conceded. "But Kozuch Theory clearly predicts that when you hit an electron linked to a proton with another one linked to a positron, the proton will decay into a neutron, the positron will neutralize… and the final wormhole will be even wider than the one we’ve just made. And there’s no room left, now, for idle speculation about Kozuch Theory being wrong. So—" He thumbed his nose at ver, then jumped to the Forge scape.

Blanca followed. The schematic ahead of them showed a wire-thin cylinder; the thickness was not remotely to scale, but the length was correctly portrayed, stretching more than ten times wider than Pluto’s orbit. All the planetary orbits were drawn in, but the inner four, Mercury to Mars, were lost in the glare of the tiny sun.

The Forge was a giant particle accelerator, consisting of over fourteen trillion free-flying components. Each one used a small light-sail to balance the sun’s slight gravitational pull and keep itself locked onto a rigid straight line 140 billion kilometers long. The sails worked off beams sent fanning out from a network of solar-powered UV lasers, orbiting the sun closer than Mercury; they also extracted the energy needed to power the accelerator.

Most of the components were individual PASER units, lined up one after the other at ten-meter intervals. They re-focused the electron beams, then boosted the energy of each particle passing through them by about 140 microjoules. That didn’t sound like much, but for one electron it was equivalent to 900 trillion volts. PASERs used the Schachter effect: a suitable material was bathed in laser light, raising its atoms into high-energy states, and when a charged particle passed along a narrow channel drilled through the material, its electric field triggered the surrounding atoms into giving up their energy. It was as if the laser primed countless tiny electronic catapults, and then the particle came along and sprung them all, one after the other, getting a small kick forward from each one.

The energy density maintained within each PASER was enormous, and Blanca had seen a recording of an early test model bursting from radiation pressure. There hadn’t been much of an explosion, though; the PASERs were tiny garnet-like crystals, each one massing less than a gram. Substantial asteroids, hundreds of meters wide, had been mined for the tens of millions of tons of raw materials needed to make the Forge, but even Carter-Zimmerman’s most gung-ho astrophysical engineers would have vetoed any design that required gutting Ceres or Vesta or Pallas.

Blanca jumped to one end of the Forge, where the scape showed a "live" image of the real equipment, albeit delayed by the 65 hours it took for the signal to reach Earth. At both ends of the linear accelerator, electron-positron pairs were created in small cyclotrons; the positrons were retained in storage rings, while the electrons were fed straight into the main accelerator. The opposing beams met in the center of the Forge, and if two electrons collided head-on, fast enough to overcome electrostatic repulsion, Kozuch Theory predicted that they’d splice wormholes. The electrons themselves would disappear without a trace—locally violating conservation of both charge and energy—but the negative charge lost would be balanced by the neutralization of the positrons at the new wormhole’s far ends, and the energy of the missing electrons would manifest itself as the mass of the two neutral particles which the positrons had become, dubbed "femtomouths" or "FMs" by the Forge group’s theorists, since they were expected to be about a femtometer wide.

Blanca was remaining cautiously skeptical, but it seemed that the predicted sequence of events had finally taken place. No instruments had witnessed the vanishing act at the center of the Forge; tracking the torrent of electrons and looking for one perfect collision among all the near misses would have been impossible. But neutral particles of exactly the right mass, heavy as specks of dust but smaller than atomic nuclei, had been caught in the laser traps surrounding both storage rings at exactly the same time.

Gabriel had followed ver, and now they moved together through the hull of the storage ring facility and hovered above the laser trap. The scape merged a camera-based view of the equipment with schematics generated from instrument readings; most unrealistically, they could see the putative FM—a black dot radiating self-important tags—being gently shuffled through the trap by the shifting gradients of luminosity, scattering UV photons just enough to let the lasers nudge it along.

It would take over an hour for the FM to be delivered from the trap into the next stage. They rushed, though not as quickly as before.

"Aren’t the rest of the Forge group watching this?" They’d entered the scape privately, invisible and oblivious to any other users; Gabriel had inflected the address that way.

"Probably."

"Don’t you want to be with them at the moment of proof?"

"Apparently not." Gabriel pressed his hand inside ver again, deeper this time; pulses of warmth spread our from the center of vis torso. Blanca turned toward him and stroked his back, reaching for the place where the fur became, if he chose, almost unbearably sensitive. C-Z culture had its problems, but in Konishi a simple exchange of pleasure phrased in this manner would have been unthinkable. The two of them were not slavishly embodied; harm remained impossible, coercion remained impossible. But Konishi had sanctified autonomy in the same absurd fashion as the statics had sanctified the pitfalls of the flesh.

The FM arrived in the gamma-ray chamber, and a series of intense pulsed bombardments began. The gamma-ray photons had wavelengths of around ten-to-the-minus-fifteen meters, roughly the same as the FM’s diameter. A photon’s wavelength had nothing to do with the size of its wormhole mouth, but it did measure how precisely you could constrain its location and aim it at a chosen target.

Blanca protested, half-seriously, "Why couldn’t you have positioned the Forge so the time lags were equal?" Gamma rays should have been emerging instantaneously from the wormhole’s other mouth, but the far end of the accelerator was three billion kilometers further from Earth than the near end, so it would be another three hours before they’d know what had happened there, 68 hours earlier.

Gabriel defended himself almost absent-mindedly "It was a compromise. Comets to avoid, gravitational effects to balance…" Blanca followed his gaze into the flickering gamma-ray glow, and knew at once what he was thinking. What they were witnessing here opened up some very strange possibilities. According to a hypothetical observer flying along the axis of the Forge toward the far end, these photons, transported faster than light, would be coming out of the wormhole before they went in. That peculiar ordering of events was largely academic—the traveler wouldn’t even know about it until photons from both ends had had time to reach ver—but if ve also happened to be carrying a wormhole mouth of vis own, linked to one in the hands of an accomplice in a second spacecraft following behind, then as the traveler flew past the far end of the Forge ve could signal the accomplice to destroy the gamma-ray source at this end… before the photons ve’d just seen emerging had ever been sent.

Once they had a second wormhole, the Forge group would be able to make this ancient thought experiment a reality. The most likely solution to the paradox involved virtual particles—the mouths of vacuum wormholes—traveling in a loop that included both the Forge wormhole and the ship-borne one. Virtual particles were constantly streaming along every available path through space-time, and though crossing ordinary space between the mouths of the two wormholes would take them a certain amount of time, moving through the ship-borne wormhole would carry them back into the past, reducing the total time needed to go around the loop. As the two spacecraft neared the point where signaling from future to past became possible, the transit time for the loop would approach zero, and each virtual particle would find an exponentially growing army of doppelgangers hard on its heels: future versions of itself which had already made the trip. As they slipped into perfect phase with each other, their rapidly increasing energy density would make the wormhole mouths implode into tiny black holes, which would then vanish in puffs of Hawking radiation.

Apart from ruling out time travel, this would have serious practical consequences: once the galaxy was crisscrossed with wormholes, there’d be loops of virtual particles threading them all, and any careless manipulation of the mouths could see the whole network annihilated.

Gabriel said, "It’s almost time. Shall we…?"

They jumped to the far end of the Forge, where the scape was showing the most recent data available: still a few minutes before the gamma-ray bombardment had begun. The second FM sat in an observation chamber, under the scrutiny of a cylindrical array of gamma-ray detectors, nudged occasionally by UV lasers to keep it perfectly centered. The faint scatter from the lasers was the only sign that the thing was really there; with no electric charge or magnetic moment, it was a far more elusive object than a single atom.

"Don’t you think we should be with the others?" Blanca had lived with the distant promises of the Forge for so long now that it was hard to be moved by this first, microscopic hint of what lay ahead. But if they really were on the threshold of a change that would shape the history of the Coalition for the next ten thousand years, it seemed like a fair excuse for public celebration.

"I thought you’d be pleased." Gabriel laughed curtly, offended. "At the end of eight centuries, we’re together for this moment. Doesn’t that mean anything to you?"

Blanca stroked his hack. "I’m deeply touched. But don’t you think you owe your colleagues—"

He disengaged from ver angrily. "All right. Have it your way. We’ll join the crowd."

He jumped. Blanca followed. As they re-entered the scape in public mode it seemed to expand dramatically; half of Carter-Zimmerman was hovering in the space above the observation chamber, and the image had been re-scaled to fit them all in.

People recognized Gabriel at once, and flocked around to congratulate him. Blanca moved aside and listened to the excited well-wishers.

"This is it! Can you imagine the gleisners' reaction, when they arrive at the next star and find that we’ve beaten them to it?" The citizen’s icon was an ape-shaped cage full of tiny yellow birds in constant flight.

Gabriel replied diplomatically, "We’ll be avoiding their targets. That was always the plan."

"I don’t mean we should explore the system in competition with them. Just leave an unmistakable sign." Blanca considered interjecting that the first few thousand wormholes they widened would be most unlikely to include any of the gleisners' immediate destinations, but then thought better of it.

On jumping to the scape, they’d synched by default to the average rate of its inhabitants, a rush of about a hundred thousand. It was fluctuating, though; some people were growing impatient, while others were trying to prolong the suspense. Blanca let verself drift with the average, enjoying the sense of being jostled through time by the whims of the crowd. Ve wandered through the scape, exchanging pleasantries with strangers, finding it hard to take the vast machinery of the observation chamber seriously so soon after experiencing it all on a scale where there’d barely been room to spread vis arms. Ve spotted Yatima in the distance, deep in conversation with other members of the Forge group, and felt an amusing surge of quasi-parental pride—even if most of the skills ve’d taught the orphan would have been more use to a Konishi Miner than a C-Z physicist.

As the moment approached, people started chanting a countdown. Blanca searched for Gabriel; he was surrounded by demonstrative strangers, but when he saw ver approaching he broke away.

"Five!"

Gabriel took vis hand. "I’m sorry."

"Four!"

He said, "I didn’t want to be with the others. I didn’t want to be with anyone but you."

"Three!"

Fear flashed in his eyes. "My outlook’s programmed to cushion me, but I don’t know how I’ll take this."

"Two!"

"One traversable wormhole, and then the rest is mass-production. I’ve made this my whole life. I’ve made this my whole purpose."

"ONE!"

"I cap, find another goal, choose another goal, but then who will I be?"

Blanca reached up and touched his cheek, not knowing what to say. Vis own outlook was much less focused; ve’d never faced a sharp transition like this.

"ZERO!"

The crowd fell silent. Blanca waited for the uproar, the cheers, the screams of triumph. Nothing. Gabriel looked down, then Blanca did too. The femtomouth was scattering the lasers' ultraviolet, as ever, but no gamma rays were emerging.

Blanca said, "The other mouth must have drifted out of the focus."

Gabriel laughed nervously. "But it didn’t. We were there, and the instruments said nothing." People around them were whispering their own theories discreetly, but their gestalt seemed more tolerantly amused than derisive. After eight centuries of setbacks, it would have been too good to be true if the Forge had delivered the definitive proof of its success at the first opportunity.

"Then there must be a calibration error. If the mouth drifted, but the instruments thought it was still at the focus, then the whole system needs to be recalibrated."

"Yes." Gabriel ran his hands through the fur of his face, then laughed. "Here I am expecting to fall off the edge of the world, and one more thing goes wrong to save me.”

"One final screw-up to smooth the transition. What more could you ask for?"

"Yeah."

"And then what?"

He shrugged, suddenly embarrassed by the whole question. "You said it yourself: linking the Forge is only the start. We haven’t wrapped the universe in wormholes yet. And at this rate, there’ll he screw-ups to smooth the transition for another eight hundred years."

Blanca spent half a gigatau exploring vis new imaginary world, fine-tuning the parameters and starting again a thousand times, but never intervening and sculpting the landscape directly. That was wicked—it made it less artful, and more mock-physical—but no one had to know. When ve opened it up to the public, people would marvel at its perfect blend of consistency and spontaneity.

Ve was sitting on the edge of a deep canyon, watching leaf-green dust clouds flow in around ver like a vivid but ethereal waterfall, when Gabriel appeared. Blanca had spent some time worrying about the problems with the Forge, but within the first megatau it had slipped from vis thoughts completely. Ve knew they’d sort it out, the way they’d sorted out every other obstacle. It was always just a matter of perseverance.

Gabriel said calmly, "Gamma rays are coming through the far end now."

"That’s wonderful! What was the problem? A misaligned laser?"

"There was no problem. We haven’t carried out any repairs. We haven’t changed a thing."

"What, the mouth just drifted back into the focus? Is it oscillating back and forth in the trap?"

Gabriel dipped his hands into the green flow. He was always sitting at the Locus, perfectly positioned. "The gamma rays we’re seeing now are the ones that went in at the start. We coded all the pulses with a time stamp, remember? Well, the first pulses to emerge had the time stamp for the gamma rays sent in five and a half days ago. They’ve taken as long to come out as if they’d crossed the ordinary space between the mouths. Exactly, down to the picosecond. The wormhole is traversable, but it isn’t a short cut. It’s a hundred and forty billion kilometers long."

Blanca absorbed this in silence. Asking if he was sure didn’t seem like a good idea; the Forge group would have spent the last few megatau searching frantically for a more palatable conclusion.

Finally, ve said, "Why? Do you have any ideas?'

He shrugged. "The only thing we can come up with that makes any sense is this: the total energy of the wormhole depends almost entirely on the size and shape of the mouths. It’s the mouths that interact with virtual gravitons; the wormhole tunnel can be as long or short as you like, and the mouths will still have exactly the same mass."

"Yes, but that’s no reason for the tunnel to grow longer, just because the mouths are moved apart in external space."

"Wait. There’s a tiny correction to the total energy that does depend on length. If the wormhole is shorter than the path through external space, then the energy of the virtual particles passing through it will be slightly higher than the normal vacuum energy. So if the wormhole is free to adjust its length to minimize that energy, the internal distance between the mouths will end up the same as the external distance."

"But the wormhole isn’t free to do that! Kozuch Theory won’t allow it to grow longer than ten-to-the-minus-thirty-five meters; in the six extra dimensions, the whole universe is no wider than that!"

Gabriel said dryly, "It seems Kozuch Theory has a few problems. First Lacerta, still unexplained. Now this." The gleisners had put a non-sentient probe into orbit around the Lacerta black hole, but it had revealed nothing about the cause of the neutron stars' collision.

They sat in silence for a while, legs hanging over the canyon’s edge, watching the green mist cascading down. In terms of a pure intellectual challenge, Gabriel couldn’t have hoped for more: Kozuch Theory would have to be completely re-assessed, or even replaced, and the instrument he’d spent the last eight hundred years helping to build would be at the center of the transformation.

It was only as a short cut to the stars that the Forge had turned out to be a complete waste of time.

Blanca said, "You’ve brought us closer to the truth. That’s never a defeat."

Gabriel laughed bitterly. "No? There’s already talk of cloning a thousand copies of Carter-Zimmerman and dispatching them all in different directions, to help us catch up with the gleisners. If the wormholes had been instantly traversable they would have bound the whole galaxy together; we could have moved from star to star as easily as we jump from scape to scape. But now we’re destined for fragmentation. A few clones of C-Z will fly off to the stars, centuries will pass… and by the time any news comes back the other polises will be past caring. We’ll all drift apart." He scooped a handful of dust forward, speeding its fall over the precipice. "I was going to build a network spanning the universe. That’s who I was: the citizen who’d put it all in the palms of our hands. Who am I now?"

"Instigator of the next scientific revolution."

"No." He shook his head slowly. "I can’t turn that corner. I can live with failure. I can live with humiliation. I can meekly follow the gleisners into space, slower than light, accepting that there’s no better way after all. But don’t expect me to take the thing that’s poisoned my dreams and embrace it as some kind of triumphant revelation."

Blanca watched him staring morosely into the distance. Ve’d been wrong, for all these centuries: the elegance of Kozuch Theory had never been enough for Gabriel. So the chance to uncover and remove its flaws was no consolation to him at all.

Blanca stood. "Come on."

"What?"

Ve reached down and took his hand. "Jump with me."

"Where?"

"Not to another scape. Here. Over the edge."

Gabriel regarded ver dubiously, but he rose to his feet. "Why?"

"It will make you feel better."

"I doubt it."

"Then do it for me."

He smiled ruefully. "All right."

They stood on the edge of the rock, feeling the dust swirl down around their feet. Gabriel said, surprised, "It makes me uneasy, just knowing that I’m going to give tip control of my icon. Must be something vestigial. You know even winged exuberants had a strong reaction against free fall? Diving was often a useful maneuver for them, but they retained an instinctive desire to put an end to it as soon as possible."

"Well, don’t panic and fly off, or I’ll never forgive you. Ready?"

"No." Gabriel craned his neck forward. "I really don’t like this."

Blanca squeezed his hand and stepped forward, and the laws of the imaginary world sent them tumbling down.

9. Degrees of freedom

Carter-Zimmerman polis, interstellar space

58 315 855 965 866 CST

21 March 4082, 8:06:03.020 UT

Blanca felt obliged to visit the Hull at least once a year. Everyone in Carter-Zimmerman knew that ve’d chosen to experience some subjective time on the trip to Fomalhaut—despite Gabriel’s decision to remain frozen for the duration—and there was really only one acceptable reason for doing that.

"Blanca! You’re awake!" Enif had spotted ver already, and he bounded toward ver on all fours across the micrometeorite-pitted ceramic, sure-footed as ever. Alnath and Merak followed, at a slightly more prudent velocity. Most of the Osvalds used embodiment software to simulate hypothetical vacuum-adapted fleshers, complete with airtight, thermally insulating hides, infrared communication, variably adhesive palms and soles, and simulated repair of simulated radiation damage. The design was perfectly functional, but since each space-going clone of Carter-Zimmerman polis was barely larger than one of these Star Puppies, having the real things as passengers was out of the question. The Hull was just a plausible fiction, a synthetic scape melding the real sky with an imaginary spacecraft hundreds of meters long; thousands of times heavier than the polis, it could only have been real if they’d postponed the Diaspora for a few millennia in order to manufacture enough antihydrogen to fuel it.

Enif almost collided with ver, but he swerved aside just in time, barely maintaining his grip. He was always showing off his finely honed Hull-skills, but Blanca wondered what the others would have done if he’d misjudged the adhesion and launched himself into space. Would they have violated the carefully simulated physics and magicked him back down? Or would they have mounted a somber rescue mission?

"You’re awake! Exactly one year later!"

"That’s right. I’ve decided to become your vernal equinox, keeping you in touch with the rhythms of the home world." Blanca couldn’t help verself; ever since ve’d discovered that the Osvalds' outlook made them lap up any old astrobabble like this as if it was dazzlingly profound, ve’d been pushing the envelope in search of whatever vestigial sense of irony might have survived their perfect accommodation to the mental rigors of interstellar travel.

Enif sighed happily, "You’ll be our dark sun rising, a nostalgic afterimage on our collective retina!" The others had caught up, and the three of them began earnestly discussing the importance of remaining in synch with the Earth’s ancient cycles. The fact that they were all fifth generation C-Z homeborn who’d never been remotely affected by the seasons didn’t seem to rate a mention. When Carter-Zimmerman polis was cloned a thousand times and the clones launched toward a thousand destinations, the vast majority of citizens taking part in the Diaspora had sensibly decided to keep all their snapshots frozen until they arrived, side-stepping both tedium and risk. If a snapshot file was destroyed en route without having been run since the instant of cloning, that would constitute no loss, no death, at all. Many citizens had also programmed their exoselves to restart them only at target systems that turned out to be sufficiently interesting, eliminating even the risk of disappointment.

At the other extreme, ninety-two citizens had chosen to experience every one of the thousand journeys, and though some were rushing fast enough to shrink each trip to a few megatau, the rest subscribed to the curious belief that flesher-equivalent subjective time was the only "honest" rate at which to engage with the physical world. They were the ones who required the most heavy-handed outlooks to keep them from going insane.

"So, what’s new? What have I missed?" Blanca showed verself on the Hull no more than once or twice a year, letting the Osvalds assume that ve was spending the rest of the time frozen. Since ve’d chosen to wake at all only on this, the shortest of the journeys, such a watered-down approach to the Diaspora Experience must have struck vis fellow passengers as consistent, if not exactly laudable.

Merak rose up on her hind legs, frowning amiably, the veins in her throat beneath her violet hide still pulsing visibly after her sprint. "You really can’t tell! Procyon’s shifted almost a sixth of a degree since you were last here! And Alpha Centauri more than twice as much!" She closed her eyes, for a moment too blissed-out to continue. "Don’t you feel it, Blanca? You must! That exquisite sense of parallax, of moving through the stars in three dimensions…"

Blanca had privately dubbed the citizens who used this outlook—most, but not all of them Star Puppies—"The Osvalds," after the character in Ibsen’s Ghosts who ends the play repeating senselessly, "The sun. The sun." The stars. The stars. When they weren’t speechless with joy over parallax shifts, they were mesmerized by the fluctuations of variable stars, or the slow orbits of a few easily resolved binaries. The polis was too small to be equipped with serious astronomical facilities, and in any case the Star Puppies stuck slavishly to their limited, mock-biological vision. But they basked in the starlight, and reveled in the sheer distance and time scales of the journey, because they’d reshaped their minds to render every detail of the experience endlessly pleasurable, endlessly fascinating, and endlessly significant.

Blanca stayed for a few kilotau, allowing Enif, Alnath, and Merak to lead ver all the way around the imaginary ship, pointing out hundreds of tiny changes in the sky and explaining what they meant, stopping now and then to show ver off to their friends. When ve finally hinted that vis time was almost up, they took ver to the nose and gazed reverently at their destination. In a year, Fomalhaut hadn’t brightened noticeably, and there were no close stars to be seen streaming away from it, so even Merak had to admit that there was nothing much to single it out.

Blanca didn’t have the heart to remind them that they’d deliberately blinded themselves to the most spectacular sign of the polis’s motion: at eight percent of lightspeed, the Doppler-shift starbow centered on Fomalhaut was far too subtle for them to detect. The scape itself was based on data from cameras with single-photon sensitivity and sub-Angstrom wavelength resolution, so the sight was there for the asking, but the idea of cheating their embodiment to absorb this information directly, or even just constructing a false-color sky to exaggerate the Doppler effect to the point of visibility, would have filled them with horror. They were experiencing the trip through the raw senses of plausible space faring fleshers; any embellishments could only detract from that authenticity, and risk leading them into the madness of abstractionism.

Ve bid them farewell until next time. They gamboled around ver, protesting noisily and pleading with ver to stay, but Blanca knew they wouldn’t miss ver for long.

Back in vis homescape, Blanca admitted to verself that ve’d actually enjoyed the visit. A brief dose of the Puppies' relentless enthusiasm always helped shake up vis perspective on vis own obsession.

Vis current homescape was a fissured, vitreous plain beneath a deep orange sky. Mercurial silver clouds just a few delta from the ground rose in updrafts, sublimated into invisible vapor, then re-condensed abruptly and sank again. The ground suffered quakes induced by forces from the clouds that had no analogue in real-world physics; Blanca was beginning to get a feel for the patterns in the sky that presaged the big ones, but the precise rules, complex emergent properties of the lower-level deterministic laws, remained elusive. This world and its seismology were just decoration and diversion, though. The reason ve’d elected to experience time on the voyage at all zig-zagged for kilodelta across the scape—and the trail of discarded Kozuch diagrams, failed attempts to solve the Distance Problem, would soon constitute the most significant feature of the plain, out-classing the fissures produced by even the strongest quakes.

Blanca hovered at the fresh end of the trail, taking stock of vis recent dismal efforts. Ve’d spent the last few megatau trying to patch an ugly system of "higher-order corrections" onto Kozuch’s original model, infinite regresses of wormholes-within-wormholes which ve’d hoped might sum to arbitrarily large, but finite, lengths, hundred-billion-kilometer fractals packed into a space twenty orders of magnitude smaller than a proton. Before that, ve’d tinkered with the process of vacuum creation and annihilation, trying to get the space-time in the wormhole to expand and contract on cue as the mouths were repositioned. Neither approach had worked, and in retrospect ve was glad that they hadn’t; these ad hoc modifications were far too clumsy to deserve to be true.

After being used to create the antihydrogen to fuel the Diaspora, the Forge had been reclaimed by the small group of particle physicists in Earth C-Z not terminally disillusioned by the failure of its original purpose. Their experiments had now probed every known species of particle down to the Planck-Wheeler length, and so long as no traversable wormholes were produced the results remained perfectly consistent with Kozuch Theory. To Blanca, this strongly suggested that Kozuch’s original identification between particle types and wormhole mouths was correct, and whatever else needed to he overhauled or thrown out, that basic idea should remain intact as the core of a revised theory.

On Earth, though, there was a growing consensus that Kozuch’s whole model had to be abandoned. The six extra dimensions which allowed the wormhole mouths their diversity were already being described as "the mathematical fiction that misled physicists for two thousand years," and theorists were urging each other to adopt a more "realistic" approach with all the puritanical vigor of scourge-wielding penitents.

Blanca accepted that it was possible that all of Kozuch Theory’s successful predictions were due to nothing but the "mirroring" of the logical structure of wormhole topology in another system altogether. The motion under gravity of an object dropped down a borehole passing through the center of an asteroid obeyed essentially the same mathematics as the motion of an object tied to the free end of an idealized anchored spring—but pushing either model too far as a metaphor for the other generated nonsense. The success of Kozuch’s model could be due to the fact that it was just an extremely good metaphor, most of the time, for some deeper physical process which was actually as different from extra-dimensional wormholes as a spring was different from an asteroid.

The trouble was, this conclusion fitted the prevailing mood in C-Z far too well: the recriminations over the failure of wormhole travel, the backlash against the other polises' continuing retreat from the physical world, and the increasingly popular doctrine that the only way to avoid following them was to anchor C-Z culture firmly to the rock of direct ancestral experience, and dismiss everything else as metaphysical indulgence. In that climate, Kozuch’s six extra dimensions could never be more than the product of a temporary misunderstanding of what was really going on.

Blanca had originally planned to spend no more than twenty or thirty megatau on the problem, then sleep for the rest of the voyage, satisfied that ve’d struggled long and hard enough to understand exactly how difficult it would be to find a solution. Ve’d guarded against investing too much hope in the prospect of helping Gabriel out of his post-Forge depression, despite fanciful visions of greeting him when he woke with the news that his soul-destroying "failure" had been transformed into the key to the physics of the next two thousand years. But the fact remained that Renata Kozuch had invented a universe of unsurpassed elegance, ruled by a set of economical and harmonious laws—and the bulletins from Earth were beginning to portray this marvelous creation as some kind of hideous mistake, as disastrous as the Ptolemaic epicycles, as wrong-headed as phlogiston and the aether. Blanca felt that ve owed Kozuch herself a spirited defense.

Ve ran vis Kozuch avatar; an image of the long-dead flesher appeared in the scape beside ver. Kozuch had been a dark-haired woman, shorter than most, sixty-two years old when she’d published her masterpiece—an anomalous age for spectacular achievement in the sciences, in that era. The avatar wasn’t sentient, let alone a faithful re-creation of Kozuch’s mind; she’d died in the early years of the Introdus, and no one really knew why she’d declined to be scanned. But the software had access to her published views on a wide range of topics, and it could read between the lines to some degree and extract a limited amount of implicit information. Blanca asked, for the thirty-seventh time, "How long can a wormhole he?"

"Half the circumference of the standard fiber." The avatar, not unreasonably, injected a hint of impatience into Kozuch’s voice. And though it paraphrased inventively, the answer was always the same: about five time ten-to-the-minus-thirty-five meters.

"The standard fiber?" The avatar gave ver something approaching a look of exasperation, but Blanca pleaded stubbornly, "Remind me." Ve had to go back to the foundations; ve had to re-examine the model’s basic assumptions and find a way to modify them that made sense of the Distance Problem, but left the fundamental symmetries of the wormhole mouths intact.

The avatar relented; in the end it always cooperated, whether Kozuch herself would have or not. "Let’s start with a two-dimensional spacelike slice through a Minkowski universe—flat and static, the simplest possible toy to play with." It created a translucent rectangle, about a delta long and half a delta wide, then bent it around so that the two halves were parallel, a hand’s width apart, one above the other. "The curvature here means nothing, of course; it’s necessary in order to construct the diagram, but physically it has no significance at all." Blanca nodded, feeling slightly embarrassed; this was like asking Carl Friedrich Gauss to recite multiplication tables.

The avatar cut two small disks out of the diagram. one in the top plane and the other directly beneath it. "If we want to connect these circles with a wormhole, there are two ways of doing it." It pasted a thin rectangular strip into the diagram, joining a small part of the top hole’s rim to the matching segment of the bottom rim. Then it extended this tentative bridge all the way around both holes, spinning it out into a complete tunnel. The tunnel assumed an hourglass shape, tapering to a waist but never pinching closed. "According to General Relativity, this solution would appear to have negative energy in some reference frames, especially if it was traversable. The two mouths could still have positive mass, though, so I pursued some tentative quantum-gravity versions of this for a while, but in the end I could never make it work as a model for stable particles."

It erased the hourglass-shaped tunnel, leaving the two holes disconnected again, then pasted a narrow strip between the left-hand side of the top rim and the right hand side of the bottom rim. As before, it extended the strip all the way around both circles, always connecting opposite sides of the rims, creating a pair of cones meeting at a point between the wormhole mouths. "This solution has positive mass. In fact, if GR held true at this scale, it would just be a pair of black holes sharing a singularity. Of course, even for the heaviest elementary particles the Schwarzschild radius is far smaller than the Planck-Wheeler length, so quantum uncertainty would disrupt any potential event horizons, and perhaps even smooth away the singularity as well. But I wanted to find a simple, geometrical model underlying that uncertainty."

"So you expressed it by adding extra dimensions. If Einstein’s equations in four dimensions can’t pin down the structure of space-time on the smallest scale, then every fixed point in the classical model must have some extra degrees of freedom."